Stabilization system and method

ABSTRACT

The disclosure relates to systems and methods of spinal stabilization. Embodiments include methods of delivering a rod having a non-circular cross-sectional profile using a wire having an accommodating non-circular cross-sectional profile to inhibit movement of a rod relative to the wire. A surgical system can comprise a first sleeve advanced via a first incision to a vertebra, a second sleeve advanced via a second incision to another vertebra, a wire having a non-circular cross-sectional profile advanced via a third incision to the vertebrae and passed through the collars of bone fastener assemblies to extend from a fourth incision. A rod or a segment of a rod having a corresponding non-circular cross-sectional profile may be aligned with the wire and advanced and coupled with the vertebrae to stabilize the spine. After the rod is securely seated in the collars, the wire may be withdrawn from the body.

TECHNICAL FIELD OF THE DISCLOSURE

The disclosure describes various spine stabilization systems andmethods, including systems and methods for inserting spinalstabilization rods in a minimally invasive surgery.

BACKGROUND OF THE DISCLOSURE

Bone may be subject to degeneration caused by trauma, disease, and/oraging. Degeneration may destabilize bone and affect surroundingstructures. For example, destabilization of a spine may result inalteration of a natural spacing between adjacent vertebrae. Alterationof a natural spacing between adjacent vertebrae may subject nerves thatpass between vertebral bodies to pressure. Pressure applied to thenerves may cause pain and/or nerve damage. Maintaining the naturalspacing between vertebrae may reduce pressure applied to nerves thatpass between vertebral bodies. A spine stabilization procedure may beperformed to maintain the natural spacing between vertebrae and promotespinal stability. Spinal stabilization may involve accessing a portionof the spine through soft tissue. Conventional stabilization systems mayrequire a large incision and/or multiple incisions in the soft tissue toprovide access to a portion of the spine to be stabilized. Conventionalprocedures may result in trauma to the soft tissue, for example, due tomuscle stripping. Spine stabilization systems for a lumbar region of thespine may be inserted during a spine stabilization procedure using aposterior spinal approach. Conventional systems and methods forposterolateral spinal fusion may involve dissecting and retracting softtissue proximate the surgical site. Dissection and retraction of softtissue may cause trauma to the soft tissue, and extend recovery time.

SUMMARY OF THE DISCLOSURE

Minimally invasive procedures and systems may reduce recovery time aswell as trauma to the soft tissue surrounding a stabilization site. Thedisclosure describes embodiments of systems and methods for spinalstabilization, particularly systems and methods that utilize a wirehaving a non-circular cross-sectional profile to deliver, preferablypercutaneously, an elongated member (e.g., a rod). According to oneembodiment, a system for stabilizing a portion of a spine comprises arod having a non-circular cross-sectional profile and a length to spanbetween two vertebrae, two bone fastener assemblies, and a wire forpercutaneous advancement of the rod to the passage in a bone fastenerassembly anchored to a vertebra. In some embodiments, the wire comprisesa non-circular cross-sectional profile complementary to the non-circularcross-sectional profile of the rod for engaging the rod to inhibitrotational movement of the rod relative to the wire. In someembodiments, each bone fastener assembly includes a pedicle screw foradvancement into a vertebra, a collar for coupling the rod to thepedicle screw, and a threaded closure member for engaging the threadedportion of the collar to couple the rod in a passage in the collar. Acollar may have two upwardly extending walls forming a passage having aprofile for receiving and accommodating a portion of the non-circularcross-sectional profile of the rod. A collar may have an opening forminga passage having a profile for receiving and accommodating a portion ofthe non-circular cross-sectional profile of the rod. In someembodiments, the non-circular cross-sectional profile of the rod mayinclude an array of surfaces, a flange, a slot, a cannulated passagealong a length of the rod, or a recessed portion along a length of therod. In some embodiments, the rod comprises two segments, wherein eachsegment has a complementary non-circular cross-sectional profile forengaging the non-circular cross-sectional profile of the wire to inhibitrotational movement of the segment relative to the wire, a surface forengagement with a collar, a leading end for displacing tissue duringadvancement of a segment along the wire, and a trailing end comprisingan engagement feature for connecting with an adjacent segment, whereinconnecting the two segments forms a rod to span a vertebral level. Insome embodiments, each segment comprises a cannulated passage through aportion thereof. In some embodiments, the cannulated passage extendsalong a central axis, is offset from a central axis, or is orientedaskew to a longitudinal axis. In some embodiments, the rod comprises acurvature, bend, or angle along a length thereof. In some embodiments,the rod comprises a recessed portion located along the length andoriented transverse to the longitudinal axis. In some embodiments, thewire has a cross-sectional profile and a curvature for engaging therecessed portion. In some embodiments, the recessed portion is orientedat a selected angle relative to the longitudinal axis or a grooveextending around at least a portion of the outer surface. In someembodiments, coupling a rod having a non-circular profile to a bonescrew comprises positioning a portion of a wire having a non-circularcross-sectional profile complementary to the rod in a first passagethrough the collar and positioning a portion of the rod in the secondpassage and engaging a closure member in the collar. In someembodiments, engaging the closure member provides sufficient clearancefor the wire to be withdrawn. In some embodiments, engaging the closuremember securely couples the wire and rod to the bone screw.

According to another embodiment, a method for stabilizing a portion of aspine comprises the steps of making a first incision for anchoring afirst bone fastener assembly in a first vertebra, making a secondincision for anchoring a second bone fastener assembly in a secondvertebra, making a third incision for entry of a wire having anon-circular cross sectional profile, making a fourth incision forexiting of the wire, advancing the wire through the third incision forpositioning near the first and second bone fastener assemblies, engaginga rod with the wire, rotating the wire to rotate the rod, and securingthe rod to the first and second bone screws, wherein the rod spans atleast one vertebral level. In some embodiments, a bone fastener assemblycomprises includes a bone screw having a threaded shank for engaging aportion of a vertebra and a head portion connected to the threadedshank, a collar with a bottom portion having an opening for receiving aportion of a bone screw and two upwardly extending walls forming a firstpassage for receiving the rod and forming a second passage for receivinga portion of a wire, a threaded portion, and a threaded closure memberthreaded for engaging the threaded portion of the collar. In someembodiments, the rod has a non-circular cross-sectional profile, whereinthe rod's non-circular cross-sectional profile is complementary to thewire's non-circular cross-sectional profile for engaging the wire toinhibit rotational movement of the rod relative to the wire. In someembodiments, the rod comprises two or more segments. In someembodiments, the method comprises engaging a first segment of a rod tothe wire, advancing the first segment along the wire to a second passagein the first collar, engaging a second segment of the rod to the wire,advancing the second segment to a second passage in the second collar,and connecting a leading end of the second segment with the trailing endof the first segment to span a vertebral level with a rod having firstand second curvatures. In some embodiments, each segment of a rodcomprises a complementary non-circular cross-sectional profile forengaging the non-circular cross-sectional profile of the wire to inhibitrotational movement of the segment relative to the wire, a surface forengagement with a collar, a leading end for displacing tissue duringadvancement of a segment along the wire, and a trailing end comprisingan engagement feature for connecting with the leading end of an adjacentsegment, wherein one or more segments form a rod that can connect to twoor more collars to span one or more vertebral levels.

According to another embodiment, the present disclosure includes amethod for advancing a rod into a body. The method may include advancinga first bone fastener assembly via a first incision in the body,anchoring the first bone fastener assembly to a first vertebra,advancing a second bone fastener assembly via a second incision in thebody, anchoring the second bone fastener assembly to a second vertebra,advancing a wire into the body via a third incision, advancing the wirethrough transverse openings in the first and second bone fastenerassemblies to define a path, advancing the wire out of the body via afourth incision, engaging a rod with the wire, and advancing the rodthrough the transverse openings in the first and second bone fastenerassemblies along the path. In some embodiments, a bone fastener assemblyincludes a bone screw having a threaded portion and a head portioncoupled to a collar. The collar may have an opening for receiving thehead portion of the bone screw and a passage oriented transverse to theopening for receiving the wire or rod or both. In some embodiments, thewire comprises a non-circular cross-sectional profile and the rodcomprises a non-circular cross-sectional profile complementary to thewire cross-sectional profile. In some embodiments, the wire maintainsthe radial orientation of the rod during advancement along the wire. Insome embodiments, the rod comprises a passage along a portion thereof.In some embodiments, the step of advancing the rod comprises moving therod along the wire. In some embodiments, the rod comprises an attachmentfeature for attaching the rod to the wire. In some embodiments, the stepof advancing the rod comprises moving the wire. In some embodiments, thestep of advancing the rod comprises advancing the rod from the thirdincision to the fourth incision. In some embodiments, the step ofadvancing the rod comprises advancing the rod from the fourth incisionto the third incision. In some embodiments, the rod comprises twosegments, wherein each segment comprises a surface for engagement with acollar, a leading end for displacing tissue during advancement throughthe body, and a trailing end comprising a connection feature forconnecting with an adjacent segment, wherein connecting the two segmentsforms a rod, wherein engaging the two connected segments to the two bonefastener assemblies spans a vertebral level.

Embodiments disclosed herein provide many advantages. For example, inembodiments of the spine stabilization system and method disclosedherein, a spinal rod is not confined to a fixed arc during insertion.

Yet another advantage provided by embodiments of the spine stabilizationsystem and method disclosed herein is that the additional componentsused for percutaneous delivery of a spinal rod can be easy to place anduse.

BRIEF DESCRIPTION OF THE FIGURES

Additional features and advantages of the embodiments will becomeapparent to those skilled in the art with the benefit of the followingdetailed description and upon reference to the accompanying drawings inwhich:

FIGS. 1 and 2 depict perspective views of embodiments of a portion of aspine stabilization system.

FIG. 3 depicts a perspective view of one embodiment of a portion of abone fastener assembly.

FIG. 4 depicts a side view of one embodiment of a portion of a bonefastener assembly.

FIG. 5 depicts a front view of one embodiment of a bone fastenerassembly with a collar that allows for angulation of a bone fastenerrelative to the collar in a conical range of motion that is symmetricalrelative to an axis that passes through a central axis of the collar anda central axis of a bone fastener.

FIG. 6A depicts a front view of one embodiment of a bone fastenerassembly with a collar that allows for angulation of a bone fastenerrelative to the collar in a conical range of motion that is notsymmetrical relative to an axis that passes through a central axis ofthe collar and a central axis of a bone fastener. The collar allowsadditional lateral bias relative to a non-biased collar.

FIG. 6B depicts a side view of one embodiment of a bone fastenerassembly with a collar that allows for angulation of a bone fastenerrelative to the collar in a conical range of motion that is notsymmetrical relative to an axis that passes through a central axis ofthe collar and a central axis of a bone fastener. The collar allowsadditional caudal or cephalid bias relative to a non-biased collar.

FIG. 7A depicts a schematic side view representation of embodiments ofbone fastener assemblies positioned in vertebrae.

FIG. 7B depicts a schematic top view representation of one embodiment ofa single-level spine stabilization system.

FIG. 8 depicts a perspective view of one embodiment of a targetingneedle.

FIG. 9 depicts a perspective view of an outer housing of a targetingneedle.

FIG. 10 depicts a perspective view of one embodiment of a member of atargeting needle.

FIG. 11 depicts a perspective view of one embodiment of a guide wire.

FIG. 12 depicts a perspective view of one embodiment of a guide wire.

FIG. 13 depicts a perspective view of one embodiment of a multi-channelsleeve.

FIG. 14 depicts a cross-sectional representation of a portion of thesleeve with the bone fastener assembly taken substantially along line14-14 of FIG. 13.

FIG. 15 depicts a perspective view of one embodiment of a single-channelsleeve.

FIG. 16 depicts a partial cross-sectional representation of oneembodiment of a sleeve coupled to a collar of a bone fastener assembly.

FIG. 17 depicts top view representation of one embodiment of a collar.

FIG. 18 depicts a partial cross-sectional representation of oneembodiment of a sleeve coupled to one embodiment of a collar of a bonefastener assembly, such as the collar depicted in FIG. 17.

FIG. 19 depicts a top view representation of one embodiment of a collar.

FIG. 20 depicts a partial cross-sectional representation of oneembodiment of a sleeve coupled to one embodiment of a collar of a bonefastener assembly, such as the collar depicted in FIG. 19.

FIG. 21 depicts a partial cross-sectional view of one embodiment of asleeve with an inner sleeve.

FIG. 22 depicts a partial cross-sectional representation of oneembodiment of a sleeve coupled to a collar of a bone fastener assembly.

FIG. 23 depicts a partial cross-sectional representation of oneembodiment of a sleeve coupled to a collar of a bone fastener assembly.

FIG. 24 depicts a partial cross-sectional representation of oneembodiment of a sleeve coupled to a collar of a bone fastener assembly.

FIG. 25 depicts a cross-sectional representation of one embodiment of ahinged sleeve coupled to a collar of a bone fastener assembly.

FIG. 26 depicts a cross-sectional representation of one embodiment of ahinged sleeve coupled to a collar of a bone fastener assembly.

FIG. 27 depicts a schematic representation of sleeve embodiments coupledto collars of a spine stabilization system.

FIG. 28 depicts a schematic representation of sleeve embodiments withconnections that allow relative movement of portions of a sleeve.

FIG. 29 depicts a perspective view of one embodiment of sleeves that arecoupled to bone fastener assemblies.

FIG. 30 depicts a schematic view of sleeve embodiments that are coupledto one embodiment of a frame.

FIG. 31 depicts a perspective view of one embodiment of a driver coupledto a bone fastener and a sleeve.

FIG. 32 depicts a partial cross-sectional view of one embodiment of abone fastener and collar coupled to a driver positioned in a dilator.

FIG. 33 depicts a side view of one embodiment of a rod having multiplesegments.

FIG. 34 depicts a side view of one embodiment of a segment of oneembodiment of a rod.

FIG. 35 depicts a side view of one embodiment of a segment of oneembodiment of a rod.

FIG. 36 depicts a side view of one embodiment of a segment of oneembodiment of a rod.

FIG. 37 depicts a side view of one embodiment of a spine stabilizationsystem illustrating a method for advancing a rod into one embodiment ofa bone fastener assembly.

FIG. 38 depicts a perspective view of one embodiment of a spinestabilization system illustrating a method for advancing a rod into oneembodiment of a bone fastener assembly.

FIGS. 39A and 39B depict perspective views of a tool designed toposition a closure member in a collar coupled to a bone fastener.

FIGS. 40A and 40B depict perspective views of a tool designed toposition a closure member in a collar coupled to a bone fastener.

FIG. 41 depicts one embodiment of a counter torque wrench coupled to asleeve.

FIG. 42 depicts one embodiment of a counter torque wrench.

FIG. 43 depicts a schematic view of the counter torque wrench shown inFIG. 42 coupled to a rod.

FIGS. 44A-44E depict schematic views of guide wire placement during aminimally invasive spine stabilization procedure.

FIGS. 45A-45D depict schematic views of tissue dilation during aminimally invasive spine stabilization procedure.

FIGS. 46A-46F depict schematic views of vertebra preparation forreceiving a bone fastener assembly during a minimally invasive spinestabilization procedure.

FIGS. 47A-47D depict schematic views of insertion of a sleeve and bonefastener assembly during a minimally invasive spine stabilizationprocedure.

FIG. 48 depicts a side view of one embodiment of a rod.

FIG. 49 depicts a side view of one embodiment of a rod.

FIG. 50 depicts a side view of one embodiment of a rod.

FIG. 51 depicts a side view of one embodiment of a rod.

FIGS. 52A-52D depict schematic views of a sleeve removal during aminimally invasive spine stabilization procedure.

Specific embodiments are shown by way of example in the drawings andwill herein be described in detail. The drawings may not be to scale. Itshould be understood that the drawings and detailed description theretoare not intended to limit the embodiments to the particular formdisclosed.

DETAILED DESCRIPTION OF THE DISCLOSURE

A spine stabilization system may be installed in a patient to stabilizea portion of a spine. Spinal stabilization may be used, but is notlimited to use, in patients having degenerative disc disease, spinalstenosis, spondylolisthesis, pseudoarthrosis, and/or spinal deformities;in patients having fracture or other vertebral trauma; and in patientsafter tumor resection. A spine stabilization system may be installedusing a minimally invasive procedure. An instrumentation set may includeinstruments and spine stabilization system components for forming aspine stabilization system in a patient.

A minimally invasive procedure may be used to limit an amount of traumato soft tissue surrounding vertebrae that are to be stabilized.Particularly, a procedure may be used to percutaneously deliver a spinalrod. In some embodiments, the natural flexibility of skin and softtissue may be used to limit the length and/or depth of an incision orincisions needed during the stabilization procedure. Minimally invasiveprocedures may provide limited direct visibility in vivo. Forming aspine stabilization system using a minimally invasive procedure mayinclude using tools to position system components in the body. Aminimally invasive procedure may be performed after installation of oneor more spinal implants in a patient. The spinal implant or spinalimplants may be inserted using an anterior procedure and/or a lateralprocedure. The patient may be turned and a minimally invasive proceduremay be used to install a posterior spine stabilization system. Aminimally invasive procedure for stabilizing the spine may be performedwithout prior insertion of one or more spinal implants in some patients.In some patients, a minimally invasive procedure may be used to installa spine stabilization system after one or more spinal implants areinserted using a posterior spinal approach. A spine stabilization systemmay be used to achieve rigid pedicle fixation while minimizing theamount of damage to surrounding tissue. In some embodiments, a spinestabilization system may be used to provide stability to two adjacentvertebrae (i.e., one vertebral level). A spine stabilization system mayinclude two bone fastener assemblies. One bone fastener assembly may bepositioned in each of the vertebrae to be stabilized. A wire may beadvanced to the bone fastener assemblies. A rod may be advanced alongthe wire and coupled and secured to the bone fastener assemblies. Asused herein, “coupled” components may directly contact each other or maybe separated by one or more intervening members. In some embodiments, asingle spine stabilization system may be installed in a patient. Such asystem may be referred to as a unilateral, single-level stabilizationsystem or a single-level, two-point stabilization system. In someembodiments, two spine stabilization systems may be installed in apatient on opposite sides of a spine. Such a system may be referred toas a bilateral, single-level stabilization system or a single-level,four-point stabilization system.

In some embodiments, a spine stabilization system may provide stabilityto three or more vertebrae (i.e., two or more vertebral levels). In atwo vertebral level spine stabilization system, the spine stabilizationsystem may include three bone fastener assemblies. One bone fastenerassembly may be positioned in each of the vertebrae to be stabilized. Awire may be advanced through an incision and passed through the bonefastener assemblies. A rod may be advanced along the wire and coupledand secured to the three bone fastener assemblies. In some embodiments,a single two-level spine stabilization system may be installed in apatient. Such a system may be referred to as a unilateral, two-levelstabilization system or a two-level, three-point stabilization system.In some embodiments, two three-point spine stabilization systems may beinstalled in a patient on opposite sides of a spine. Such a system maybe referred to as a bilateral, two-level stabilization system or atwo-level, six-point stabilization system. In some embodiments,combination systems may be installed. For example, a two-pointstabilization system may be installed on one side of a spine, and athree-point stabilization system may be installed on the opposite sideof the spine. The composite system may be referred to a five-pointstabilization system. Minimally invasive procedures may reduce trauma tosoft tissue surrounding vertebrae that are to be stabilized. Only smallopenings may need to be made in a patient. For example, for asingle-level stabilization procedure on one side of the spine, thesurgical procedure may be performed through four small incisions formedin the skin of the patient.

Components of spine stabilization systems may be made of materialsincluding, but not limited to, titanium, titanium alloys, stainlesssteel, ceramics, and/or polymers. Some components of a spinestabilization system may be autoclaved and/or chemically sterilized.Components that may not be autoclaved and/or chemically sterilized maybe made of sterile materials. Components made of sterile materials maybe placed in working relation to other sterile components duringassembly of a spine stabilization system. Spine stabilization systemsmay be used to correct problems in lumbar, thoracic, and/or cervicalportions of a spine. Various embodiments of a spine stabilization systemmay be used from the C1 vertebra to the sacrum. For example, a spinestabilization system may be implanted posterior to the spine to maintaindistraction between adjacent vertebral bodies in a lumbar portion of thespine.

Recently, it has become increasingly popular to insert spinal fixationrods percutaneously. One existing system is a sextant or tripod thatdelivers a fixation rod via a fixed trajectory along a fixed arc (i.e.,such systems have a fixed pivot point). One problem is that such systemsdo not easily accommodate procedures in which the spinal curvature doesnot easily align along an arc achievable by the sextant.

Embodiments of the present disclosure may be used in a wide variety ofmedical applications where the minimally invasive implantation of a rodmay be desirable. The systems and methods described herein may findutility in medical procedures where it is desirable to construct a spinefixation system having selected curvature.

FIG. 1 illustrates one embodiment of a portion of a spine stabilizationsystem, which comprises bone fastener assembly 102 and rod 104 (shown ina cross-sectional view). As will be described below in more detail, wire400 (shown in a cross-sectional view in conjunction with rod 104) isuseful for the percutaneous advancement of rod 104 into the body andthrough collar 112 of bone fastener assembly 102 for constructing aspine stabilization system without requiring a sextant. Wire 400 can beformed of titanium, titanium alloys, stainless steel, ceramics,polyethersulfone, PEEK, polymers or other biocompatible material and canbe formed as a single piece of material or as multiple pieces that arecoupled together. As shown in FIG. 1, wire 400 may have a non-circularcross-sectional profile. Wire 400 may include two or more surfaces 400a-400 n. For example, FIG. 1 depicts one embodiment in which wire 400may have a cross-sectional profile defined by surfaces 400 a, 400 b, 400c, 400 d, 400 e, 400 f, 400 g and 400 h. While wire 400 is shown in FIG.1 as having curved sides with different radiuses of curvature andstraight sides of different lengths, wire 400 can have a variety ofshapes including, but not limited to, a rectangular profile, atrapezoidal opening, a square profile, an ovoid profile, an egg-shapedprofile, a tapered profile, and combinations and/or portions thereof.

Rod 104 may have a cross-sectional profile that is complementary to thecross-sectional profile of wire 400. As shown in FIG. 1, rod 104 mayhave a cross-sectional profile defined by surfaces 104 a, 104 b and 104c to enable rod 104 to engage wire 400. Advantageously, thecross-sectional profile of wire 400 may inhibit rotational movement ofrod 104 relative to wire 400 so the orientation of rod 104 is maintainedduring the advancement of rod 104 into the body.

As shown in FIG. 1, collar 112 may have transverse opening 116 forreceiving wire 400 and rod 104. In FIG. 1, transverse opening 116 mayhave a profile that allows wire 400 and/or rod 104 to pass throughcollar 112 in only one orientation. Advantageously, components of spinalsystem 100 may be advanced along wire 400 such that they reach collar112 in a selected orientation.

As shown in FIGS. 1 and 2, opening 116 of collar 112 may have twodifferent sections. A first section, 116A, may be small enough to allowpassage of wire 400 only. A second section, 116B may allow passage ofwire 400 and rod 104.

In some procedures, it may be desirable to index rod 104 or tools onwire 400. FIG. 2 depicts a perspective view of one embodiment of aportion of spine stabilization system 100 in which rod 104 may beindexed on wire 400. To index rod 104 on wire 400 in FIG. 2, rod 104 maybe rotated such that surface 104 a contacts any of surfaces 400 a-400 f.An advantage of this embodiment is the capability to percutaneouslyconstruct rod 104 having a desired curvature. Indexing rod 104 on wire400 may be particularly useful for embodiments in which rod 104 isformed by two or more segments, discussed below.

FIG. 3 depicts one embodiment of bone fastener assembly components.Components of bone fastener assembly 102 depicted in FIG. 3 may include,but are not limited to, bone fastener 108 and collar 112. Bone fastener108 may be used to anchor bone fastener assembly 102 to a vertebra.

A bone fastener may be, but is not limited to, a bone screw, a ringshank fastener, a barb, a nail, a brad, or a trocar. Bone fastenersand/or bone fastener assemblies may be provided in various lengths in aninstrumentation set to accommodate variability in vertebral bodies. Forexample, an instrumentation set for stabilizing vertebrae in a lumbarregion of the spine may include bone fastener assemblies with lengthsranging from about 30 mm to about 75 mm in 5 mm increments. A bonefastener assembly may be stamped with indicia (i.e., printing on a sideof the collar). In some embodiments, a bone fastener assembly or a bonefastener may be color-coded to indicate a length of the bone fastener.In certain embodiments, a bone fastener with a 30 mm thread length mayhave a magenta color, a bone fastener with a 35 mm thread length mayhave an orange color, and a bone fastener with a 55 mm thread length mayhave a blue color. Other colors may be used as desired. Each bonefastener provided in an instrumentation set may have substantially thesame thread profile and thread pitch. In one embodiment, the thread mayhave about a 4 mm major diameter and about a 2.5 mm minor diameter witha cancellous thread profile. In certain embodiments, the minor diameterof the thread may be in a range from about 1.5 mm to about 4 mm orlarger. In certain embodiments, the major diameter of the thread may bein a range from about 3.5 mm to about 6.5 mm or larger. Bone fastenerswith other thread dimensions and/or thread profiles may also be used. Athread profile of the bone fasteners may allow bone purchase to bemaximized when the bone fastener is positioned in vertebral bone.

Bone fastener 108 may include a shank, a head, and a neck. The shank mayinclude threading. In some embodiments, threading may include aself-tapping start. A self-tapping start may facilitate insertion ofbone fastener 108 into vertebral bone. The head of bone fastener 108 mayinclude various configurations to engage a driver that inserts the bonefastener into a vertebra. In some embodiments, the driver may also beused to remove an installed bone fastener from a vertebra. In someembodiments, the head may include one or more tool portions. Toolportions may be recesses and/or protrusions designed to engage a portionof the driver. In some embodiments, bone fastener 108 may be cannulatedfor use in a minimally invasive procedure. The neck of bone fastener 108may have a smaller diameter than adjacent portions of the head and theshank. The diameter of the neck may fix the maximum angle that thecollar of the bone fastener assembly can be rotated relative to bonefastener 108.

In some embodiments, the neck may be sized to allow up to about 40° ormore of angulation of the collar relative to the bone fastener. In someembodiments, the neck may be sized to allow up to about 30° ofangulation of the collar relative to the bone fastener. In someembodiments, the neck may be sized to allow up to about 20° ofangulation of the collar relative to the bone fastener.

As used herein, the term “collar” includes any element that wholly orpartially encloses or receives one or more other elements. A collar mayenclose or receive elements including, but not limited to, a bonefastener, a closure member, a ring, and/or a rod. In some embodiments, acollar may couple two or more other elements together (e.g., a rod and abone fastener). A collar may have any of various physical forms. In someembodiments, a collar may have a “U” shape, however it is to beunderstood that a collar may also have other shapes. A collar may beopen or closed. A collar having a slot and an open top, such as collar112 shown in FIG. 3, may be referred to as an “open collar.” A bonefastener assembly that includes an open collar may be referred to as an“open fastener.” In some embodiments, a rod may be top loaded into theopen fastener. A closure member may be coupled to the collar to securethe rod to the open fastener.

A collar that does not include a slot and an open top, such as depictedin FIGS. 1 and 2, may be referred to as a “closed collar.” A spinalimplant that includes a closed collar may be referred to as a “closedimplant.” A closed collar may include an aperture, bore, or otherfeature in side surfaces for accommodating other components of astabilization system (e.g., a rod or wire, discussed below). A setscrewmay be used to securely couple a rod to a closed implant.

Collar 112 may include a body and arms. The arms may extend from thebody. The body of collar 112 may be greater in width than a width acrossthe arms of collar 112 (i.e., the body may have a maximum effectiveouter diameter greater than a maximum effective outer diameter of thearms). A reduced width across the arms may allow a detachable member tobe coupled to the arms without substantially increasing a maximumeffective outer diameter along a length of collar 112. Thus, a reducedwidth across the arms may reduce bulk at a surgical site. A height ofcollar body may range from about 3 millimeters (mm) to about 7 mm. Inone embodiment, a height of the collar body is about 5 mm. The collarbody may include an opening in a lower surface. Inner surfaces and/orouter surfaces of collar 112 may be surface treated or include coatingsand/or coverings to modify frictional properties or other properties ofthe collar. Inner surfaces of the arms may include a modified thread.The modified thread may engage a complementary modified thread of aclosure member to secure a rod to a bone fastener assembly. The modifiedthread may have a constant pitch or a variable pitch. A height and awidth of the arms may vary. The arms may range in height from about 8 mmto about 15 mm. In one embodiment, a height of the arms is about 11 mm.A width (i.e., effective diameter) of the arms may range from about 5 mmto 14 mm. The arms and the collar body may form a slot. The slot may besized to receive a rod. A slot may include, but is not limited to, anelongated opening of constant width, an elongated opening of variablewidth, a rectangular opening, a trapezoidal opening, a circular opening,a square opening, an ovoid opening, an egg-shaped opening, a taperedopening, and combinations and/or portions thereof. In some embodiments,a first portion of the slot may have different dimensions than a secondportion of the slot. In certain embodiments, a portion of a slot in thefirst arm may have different dimensions than a portion of a slot in thesecond arm.

When rod 104 is positioned in a slot, a portion of rod 104 may contact ahead of bone fastener 108 positioned in collar 112. The arms may includeridges or flanges. Flanges may allow collar 112 to be coupled to adetachable member so that translational motion of collar 112 relative tothe detachable member is inhibited. Flanges may also include notches. Amovable member of a detachable member may extend into a notch. When themovable member is positioned in a notch, a channel in the detachablemember may align with a slot in collar 112. With the movable memberpositioned in a notch, rotational movement of collar 112 relative to thedetachable member may be inhibited.

In some embodiments, a bone fastener assembly may be a fixed anglefastener. FIG. 4 depicts one embodiment of a fixed angle bone fastener.Collar 112 and bone fastener 108 may be formed as a unitary bonefastener assembly 102. A fixed angle fastener may be positioned as thefirst bone fastener assembly inserted into a vertebra.

FIG. 5 depicts bone fastener assembly 102 with central axis 158 ofcollar 112 aligned with central axis 160 of bone fastener 108. Bonefastener 108 may be angulated in a symmetrical conical range of motioncharacterized by angle α about the aligned axes. Bone fastener 108 maybe constrained from motion outside of limit axis 162 by contact betweenneck 120 of bone fastener 108 and collar 112. Alignment of axis 160 ofbone fastener 108 with central axis 158 of collar 112 may be considereda neutral position relative to the range of motion. The alignment is aneutral position because bone fastener 108 may be angulated an equalamount in any direction from central axis 158. When a driver is insertedinto bone fastener 108, axis 160 of bone fastener 108 may besubstantially aligned with axis 158 of collar 112 to facilitateinsertion of the bone fastener into a vertebral body. In certainembodiments, a range of motion of a collar may be skewed from a fullconical range of motion relative to aligned central axes of the collarand a bone fastener coupled to the collar. In some embodiments, a distalend of a collar may be shaped to skew, or bias, the range of motion fromthe range of motion depicted in FIG. 8.

FIGS. 6A and 6B depict bone fastener assemblies 102 with biased collars112. Body 140 of biased collar 112 may be shaped to restrict relativemovement of bone fastener 108 (and/or the collar) to a skewed conicalrange of motion defined by limit axes 162. As depicted by limit axes 162in FIG. 6A, a first arm 142 of collar 112 may approach bone fastener 108more closely than a second arm of the collar. Similarly, as suggested bylimit axes 162 in FIG. 6B, collar 112 may be oriented such that the slotformed by arms 142 may not be parallel (e.g., an opening on one side ofcollar 112 may be higher than a second opening on the other side). Otherbiased collars may be designed to selectively restrict relative movementof collars and/or bone fasteners. In some embodiments, a biased collarmay be attached to a detachable member such that a surgeon performing aminimally invasive procedure may selectively align the portion of thecollar with the greater range of motion as needed. For example, thecollar depicted in FIGS. 6A-6B may be coupled to a single-level (e.g.,C-shaped) sleeve so that the side of the collar (i.e., the side of theslot) with a larger range of motion is positioned next to a channelopening of the sleeve.

When a biased collar of a bone fastener assembly is coupled to adetachable member and a drive mechanism is coupled to a bone fastener ofthe bone fastener assembly, central axis 158 of collar 112 may alignwith central axis 160 of bone fastener 108 to facilitate insertion ofthe bone fastener into bone. In some embodiments, the bias of the collarmay be so large that a flexible drive member is needed to drive the bonefastener into bone. In some embodiments, one or more biased collars maybe used in a spine stabilization system. The spine stabilization systemsmay be single-level systems or multi-level systems. Biased collars maybe used to accommodate the increasing angle of the pedicle corridor foreach lumbar vertebra. The angle may increase by about five degrees foreach successive lumbar vertebra.

FIGS. 7A and 7B depict inferior and posterior views of a single-levelspine stabilization system including bone fastener assembly 102A coupledto pedicle 164A and vertebra 166A and bone fastener assembly 102Bcoupled to pedicle 164B and vertebra 166B. A bone fastener of bonefastener assembly 102A may engage pedicle 164A at pedicle angle φArelative to sagittal plane 168. Pedicle angle φA may range between about13° and about 17°. Collar 112A of bone fastener assembly 102A may beunbiased. Pedicle angle φB may range between about 18° and about 22°.Collar 112B may have a bias angle β of about 5°. Bone fastener assembly102B may engage pedicle 164B at pedicle angle φB. Because the bias ofcollar 112B is approximately equal to the difference between the pedicleangles of the two vertebrae, slots 150A and 150B in bone fastenerassemblies 102A and 102B, respectively, may be generally aligned whenboth bone fasteners are in neutral positions. Angulation of either orboth collars of the bone fastener assemblies may allow fine adjustmentof engagement angles of the bone fasteners. In addition, collarangulation may allow adjustment in the orientation of bone fasteners ina sagittal plane (i.e., to conform to lordosis of a spine) while stillallowing the collars to be easily coupled with rod 104. Rod 104 may bedisposed in slots 150A and 150B and secured by closure members.

In some embodiments, a flexible driver or a polyaxial driver (e.g., adriver with a universal joint) may be used to drive the heads of thebone fasteners from a position that is off axis from the bone fastenersto reduce the size of an opening of the body needed to implant the spinestabilization system. A closure member may be coupled to a collar of abone fastener assembly to fix a rod positioned in the collar to the bonefastener assembly. In some embodiments, a closure member may becannulated. In certain embodiments, a closure member may have a solidcentral core. A closure member with a solid central core may allow morecontact area between the closure member and a driver used to couple theclosure member to the collar. A closure member with a solid central coremay provide a more secure connection to a rod than a cannulated closuremember by providing contact against the rod at a central portion of theclosure member as well as near an edge of the closure member.

In one embodiment, a bone fastener assembly and a closure member may becoupled with a running fit. A running fit (i.e., a fit in which partsare free to rotate) may result in predictable loading characteristics ofa coupling of bone the fastener assembly and the closure member.Predictable loading characteristics may facilitate use of a closuremember with a break-off portion designed to shear off at a predeterminedtorque. A running fit may also facilitate removal and replacement ofclosure members. In some embodiments, a closure member may include aninterference fit (e.g., crest-to-root radial interference). In oneembodiment, a position (i.e., axial position and angular orientation) ofa modified thread of a collar may be controlled, or “timed,” relative toselected surfaces of the collar. For example, a modified thread form maybe controlled relative to a top surface of a collar and an angularorientation of the slots of the collar. In some embodiments, positionsof engaging structural elements of other coupling systems (e.g., threadforms) may be controlled. Controlling a position of a modified threadform may affect a thickness of a top modified thread portion of acollar. In one embodiment, a position of a modified thread form may beselected such that the thickness of the leading edge of a top modifiedthread portion is substantially equal to the full thickness of the restof the modified thread. Controlling a position of a modified thread formof a collar may increase a combined strength of engaged modified threadportions for a collar of a given size (e.g., wall height, modifiedthread dimensions, and thread pitch). Controlling a position of themodified thread form may reduce a probability of failure of modifiedthread portions, and thus reduce a probability of coupling failurebetween a collar and a closure member. Controlling the position of amodified thread form in a collar of a bone fastener assembly mayincrease a combined strength of engaged collar and closure membermodified thread portions such that failure of the modified threadportions does not occur prior to the intended shearing off of a toolportion of the closure member. For example, a tool portion of a closuremember may be designed to shear off at about 90 in-lbs of torque, whilethe combined modified thread portions may be designed to withstand atorque on the closure member of at least 120 in-lbs.

If a thickness of a modified thread portion of a given size and profileis reduced below a minimum thickness, the modified thread portion maynot significantly contribute to the holding strength of the modifiedthread of a collar. In one embodiment, a position of a modified threadform of a collar may be controlled such that a thickness of a topmodified thread portion is sufficient for the portion to increase aholding strength of the collar. In one embodiment, a top modified threadportion may have a leading edge thickness of about 0.2 mm. In oneembodiment, a position of a modified thread form of a collar may beselected to ensure that a closure member engages a selected minimumnumber of modified thread portions on each arm of the collar. In oneembodiment, at least two modified thread portions having a fullthickness over width w of a collar arm may be engaged by a closuremember at each arm. Alternatively, a closure member may engage parts ofthree or more modified thread portions on each arm, with the total widthof the portions equal to at least two full-width portions. Allowancesmay be made for tolerances in the components (e.g., diameter of the rod)and/or anticipated misalignment between the components, such asmisalignment between a rod and a slot. In one embodiment, asubstantially equal number of modified thread portions in each arm mayengage the closure member when a rod is coupled to a bone fastenerassembly.

Various instruments may be used in a minimally invasive procedure toform a spine stabilization system in a patient. The instruments mayinclude, but are not limited to, positioning needles, guide wires,dilators, bone awls, bone taps, sleeves, drivers, and mallets. Theinstruments may be provided in an instrumentation set. Theinstrumentation set may also include components of the spinestabilization system. The components of the spine stabilization systemmay include, but are not limited to, bone fastener assemblies of varioussizes and/or lengths, rods, and closure members. Instruments used toinstall a spine stabilization system may be made of materials including,but not limited to, stainless steel, titanium, titanium alloys,ceramics, and/or polymers. Some instruments may be autoclaved and/orchemically sterilized. Some instruments may include components thatcannot be autoclaved or chemically sterilized. Components of instrumentsthat cannot be autoclaved or chemically sterilized may be made ofsterile materials. The sterile materials may be placed in workingrelation to other parts of the instrument that have been sterilized.

A targeting needle may be used to locate an entry point in a vertebralbody for a bone fastener of a bone fastener assembly. In someembodiments, the targeting needle may be a bone marrow biopsy needle.FIG. 8 depicts one embodiment of targeting needle 198. Targeting needle198 may include outer housing 200 and member 202.

FIG. 9 depicts one embodiment of outer housing 200. Outer housing 200may include hollow shaft 204 and handle 206. Scale markings 208 may beprinted, etched, or otherwise placed on hollow shaft 204. Scale markings208 may be used to approximate a length of a bone fastener needed for avertebra. Handle 206 may provide a grip that allows a user to manipulatethe targeting needle. Handle 206 may include threaded portion 210.Threaded portion 210 may couple to threading on a portion of a targetingneedle member to secure the member to outer housing 200.

FIG. 10 depicts one embodiment of member 202 of a targeting needle.Member 202 may include point 212 and cap 214. Point 212 may be placedthrough a hollow shaft of an outer housing of the targeting needle. Cap214 may include threading 216. Member 202 may be rotated relative to theouter housing to couple threading 216 with threading in a handle of theouter housing. In some embodiments, the member may be coupled to theouter housing by another type of connection system (e.g., by placementof a key in a keyway). With member 202 positioned in an outer housing,point 212 may extend from a distal end of a hollow shaft of the outerhousing. Cap 214 may be used as an impact surface for driving thetargeting needle in bone.

FIG. 11 and FIG. 12 depict embodiments of guide wire 218. Guide wire 218may be an 18-gauge K-wire. Guide wire 218 may pass down a shaft of atargeting needle outer housing. Guide wire 218 may be from about 15 cmto about 65 cm in length. In some embodiments, guide wires 218 providedin an instrumentation set are about 46 cm in length. The length of guidewire 218 may allow a surgeon and/or assistants to hold at least oneportion of guide wire 218 at all times when guide wire 218 is insertedinto vertebral bone, even during insertion, use, and removal ofinstruments along a length of guide wire 218. Guide wire 218 that can beheld continuously during a surgical procedure may inhibit removal oradvancement of guide wire 218 from a desired position during a minimallyinvasive surgical procedure.

As depicted in FIG. 11, a distal end of guide wire 218 may include point220. Point 220 may facilitate insertion of the distal end of guide wire218 into vertebral bone. As depicted in FIG. 12, a distal end of guidewire 218 may not be pointed. A position of an unpointed guide wire 218in bone may be easier to maintain during a spine stabilizationprocedure.

Dilators may be used during a minimally invasive surgical procedure topush aside tissue and create space to access vertebral bone. In someembodiments, four tissue dilators of increasing diameter may be used toestablish sufficient working space to accommodate instruments and spinestabilization system components. In some embodiments, especially for amid-vertebra or for mid-vertebrae of a multi-level stabilization system,only three dilators may be needed to form sufficient working space.Dilators in an instrumentation set may increase in diameterincrementally by a selected amount. For example, outside diameters ofdilators in an instrumentation set may increase sequentially byincrements of about 0.5 mm.

A detachable member for a single-level vertebral stabilization systemmay include one or more channels in a wall of the detachable member toallow access to an adjacent vertebra. For some single-level vertebralstabilization procedures, only single-channel detachable members (i.e.,detachable members with a single channel in a wall of the detachablemember) may be used. For other single-level vertebral stabilizationprocedures, one or more multi-channel detachable members (i.e.,detachable members with two or more channels in a wall of the detachablemember) may be used. Channels may provide flexibility to or enhanceflexibility of a multi-channel detachable member. In some embodiments, aproximal portion of a multi-channel detachable member may have a solidcircumference. A region of solid circumference in a multi-channeldetachable member may enhance stability of the multi-channel detachablemember. In some embodiments, a multi-channel detachable member may belonger than a single-channel detachable member.

A detachable member used at a middle vertebra in a multi-levelstabilization procedure may be a multi-channel detachable member.Channels in a multi-channel detachable member may allow access toadjacent vertebrae from a middle vertebra. A detachable member used atan end vertebra of a multi-level stabilization system may be asingle-channel detachable member or a multi-channel detachable member. Asystem for coupling a bone fastener assembly to a multi-channeldetachable member may include a limiter that inhibits spreading of armsof the detachable member to inhibit release of the bone fastenerassembly from the detachable member.

A channel in a wall of a detachable member may allow access to avertebra that is to be stabilized with a spine stabilization systembeing formed. In some embodiments, a single-channel detachable membermay be coupled to a bone fastener assembly to be inserted into vertebralbone of a first vertebra. The single-channel detachable member may allowaccess to a second vertebra from the first vertebra. In otherembodiments, a multi-channel detachable member may be coupled to a bonefastener assembly to be inserted into vertebral bone of a firstvertebra. The multi-channel detachable member may allow access from thefirst vertebra to adjacent vertebrae.

Instruments may access a bone fastener assembly through a passage in adetachable member. In some embodiments, a channel in a wall of adetachable member may extend a full length of the detachable member. Insome embodiments, especially in embodiments of multi-channel detachablemembers, a channel in a wall of a detachable member may extend only aportion of the length of the detachable member. In some embodiments, achannel in a wall of a detachable member may extend 25%, 50%, 75%, 80%,90%, 95% or more of the length of the detachable member.

A channel in a detachable member may be any of a variety of shapes. Insome embodiments, a channel may be a linear opening parallel to alongitudinal axis of the detachable member. In some embodiments, achannel may have a non-linear shape including, but not limited to, ahelical pattern, an arc, an “L” shape, or an “S” shape.

Movable members may extend through portions of a detachable memberproximate a channel in the detachable member. Movable members may engagenotches in a collar to establish a radial orientation of the detachablemember on the collar and/or to inhibit rotation of the collar relativeto the detachable member. A distal end of a movable member may be flat,curved, or angled. In some embodiments, a distal end of a movable membermay be threaded. In other embodiments, a distal end of a movable membermay be a projection that engages an opening in a collar. In someembodiments, an upper surface of a collar and/or a surface of a distalend of a movable member may be textured to inhibit rotation of thecollar relative to the detachable member. In certain embodiments, aproximal end of a movable member may include a tool engaging portion. Atool engaging portion may include, but is not limited to, a hex section,a hexalobular section, a tapered section, a bead, a knot, a keyedopening, a coating, a threading, and/or a roughened surface for engaginga drive that rotates or otherwise displaces the movable member.

A cross section transverse to a longitudinal axis of a detachable membermay have shapes including, but not limited to, circular, ovoid, square,pentagonal, hexagonal, and combinations thereof. In some embodiments, adetachable member may be hollow. In certain embodiments, a thickness ofa hollow detachable member may be uniform. In certain embodiments, athickness of a hollow detachable member may vary along the length of thedetachable member. A detachable member with a passage extendinglongitudinally from a first end of the detachable member to a second endof the detachable member may be referred to as a “sleeve”.

FIG. 13 depicts one embodiment of sleeve 244. Sleeve 244 may be amulti-channel sleeve. Sleeve 244 may include wall 246, channels 248,passage 250, movable members 252, and flange 254. Channels 248 mayextend from a distal end of sleeve 244 through a portion of wall 246.Passage 250 may allow instruments to be positioned and used tomanipulate a bone fastener assembly that is coupled to a distal end ofsleeve 244. Movable members 252 may be part of a system that couples abone fastener assembly to sleeve 244. In some embodiments, movablemembers 252 may include tool engaging portion 256. A driver may bepositioned in tool portion 256. The driver (e.g., a hex wrench) may beused to extend or retract a distal end of movable member 252. A distalend of sleeve 244 may include flange 254 that mates with a complementaryflange on a collar of a bone fastener assembly. A distal end of sleeve244 may be tapered to reduce bulk (e.g., reduce spin diameter) at asurgical site.

FIG. 14 depicts a cross-sectional representation of a portion of sleeve244 with bone fastener assembly 102 and rod 104. Distal ends of movablemembers 252 may extend into notches in collar 112. Portions of walls 246of sleeve 244 may include threading. Portions of movable members 252 mayinclude threading complementary to threaded portions of walls 246.Threading of movable members 252 may engage threading in walls 246 suchthat rotation of the movable members advances or retracts the movablemembers relative to the walls.

As shown in FIG. 14, collar 112 may be designed such that rod 104 liesbelow a distal end of sleeve 244. Coupling sleeve 244 to collar 112above rod 104 may reduce bulk at a surgical site. With rod 104 coupledto collar 112 below a distal end of sleeve 244, the sleeve may beremoved without interference from the rod of a spine stabilizationsystem.

FIG. 15 depicts one embodiment of sleeve 244. Sleeve 244 may be asingle-channel sleeve for use in single-level or multi-level spinestabilization procedures. Sleeve 244 may be used at the outermostvertebrae to be stabilized during installation of a multi-levelvertebral stabilization system. Sleeve 244 may be coupled to a collar ofa bone fastener assembly with movable members 252 and/or flange 254.Instruments may be inserted through passage 250 of sleeve 244 to accessan anchored bone fastener assembly coupled to the sleeve.

A sleeve may be coupled to a bone fastener assembly in various ways toinhibit movement of the sleeve relative to a collar of the bone fastenerassembly. A system used to couple the sleeve to the bone fastenerassembly may inhibit rotation and translation of the sleeve relative tothe collar.

A detachable member may be coupled to a collar of a bone fastenerassembly in various ways. When a detachable member is coupled to acollar, rotation and translation of the detachable member relative tothe collar may be inhibited. A system used to couple a detachable memberand collar should be simple, inexpensive to implement, and should notsignificantly weaken the mechanical strength of the collar and/or thedetachable member. Detachable members may be coupled to collars usingvarious coupling systems including, but not limited to, flanges,threaded connections, interlocking connections (e.g., ratchetingconnection systems), and/or interference fits.

In one embodiment of an interlocking connection system, a detachablemember may include an opposing pair of deflectable arms. Eachdeflectable arm may include a tooth. The deflectable arms may be forcedoutwards during coupling of a collar to the detachable member. When thecollar is coupled to the detachable member, the deflectable arms may bepositioned in channels in the collar, with the teeth positioned inindentions in the collar. The presence of the deflectable arms in thechannels of the collar may inhibit rotation and translation of thedetachable member relative to the collar. Separation of the detachablemember from the collar may be achieved by insertion of an expander inthe detachable member. The expander may be used to force the deflectablearms outwards and expel the teeth from the indentions.

FIGS. 16-26 depict embodiments of sleeves coupled to bone fastenerassemblies. In each bone fastener assembly/sleeve embodiment depicted inFIGS. 16-24 and FIG. 26, rod 104 and wire 400 positioned in collar 112of bone fastener assembly 102 would lie below distal end 427 of sleeve244. In some embodiments, seating rod 104 may be accomplished byadvancing rod 104 over a wire (e.g., See FIG. 37 described below).Having rod 104 and wire 400 below the distal end of sleeve 244 reducesbulk at the surgical site. With sleeve 244 positioned above rod 104,interference of the secured rod 104 or wire 400 with sleeve 244 isavoided during removal of sleeve 244.

FIG. 16 depicts a cross-sectional representation of sleeve 244 includingsleeve flange 254. Sleeve 244 may be rotated onto collar 112 until slot150 aligns with channel 248. Sleeve flange 254 may engage flange 154 ofcollar 112 to inhibit translation of sleeve 244 relative to collar 112of bone fastener assembly 102. Wire 400 and rod 104 may be advancedthrough slot 150 and positioned in collar 112 below distal end 427 ofsleeve 244.

In some detachable member and collar coupling embodiments, thedetachable member and the collar may include members that work togetherto inhibit radial expansion of walls of the detachable member. In somedetachable member and collar coupling embodiments, a detachable membermay include a protrusion that mates with a complementary groove in acollar. Alternatively, a detachable member may include a groove thatmates with a complementary protrusion of a collar.

In some embodiments, a detachable member and/or a collar may include alocking system to inhibit rotation of the detachable member relative tothe collar. The locking system may be, but is not limited to, threading,interference fits, frictional engagement, or a press-fit connection. Insome embodiments, a locking system may inhibit translation and/orrotation of a detachable member relative to a collar.

FIG. 17 depicts a top view representation of one embodiment of collar112 of a bone fastener assembly. Collar 112 includes openings 260. Insome embodiments, openings 260 may be threaded. In some embodiments,openings 260 may not include threading. The body of collar 112 adjacentto openings 260 may include extra material to provide strength to thecollar.

FIG. 18 depicts a partial cross-sectional representation of oneembodiment of sleeve 244 coupled to one embodiment of collar 112, suchas collar 112 depicted in FIG. 18. Distal end portions of movablemembers 252 may extend into openings 260. When distal end portions ofmovable members 252 are positioned in openings 260, rotational movementof sleeve 244 relative to collar 112 may be inhibited. Sleeve 244 mayinclude flange 254. Flange 254 may engage flange 154 of collar 112 toinhibit translation of sleeve 244 relative to the collar. In oneembodiment in which distal end portions of movable members in a sleeveare threaded and openings in the collar are threaded, rotation andtranslation of the collar relative to the sleeve may be inhibited whendistal end portions of the movable members are positioned in theopenings. Wire 400 and rod 104 may be advanced through slot 150 incollar 112 and positioned below distal end of sleeve 244. As depicted inFIG. 18, portion 270 of movable member 252 may include threading.Threading of portion 270 may engage threading in wall 246 of sleeve 244.Engagement of threading of portion 270 with threading in wall 246 mayallow distal end portion of movable member 252 to advance towards, orretract from, a distal end of sleeve 244 when the movable member isrotated.

FIG. 19 depicts a top view representation of one embodiment of collar112 of a bone fastener assembly. Collar 112 may include notches 156.FIG. 20 depicts a partial cross-sectional representation of oneembodiment of sleeve 244 coupled to one embodiment of collar 112, suchas the collar depicted in FIG. 19. Distal end portions of movablemembers 252 of sleeve 244 may be extended and positioned in notches 156of collar 112. An interference fit between the distal end portions ofmovable members 252 and the body of collar 112 that defines the notchesmay inhibit rotation of sleeve 244 relative to the collar. Wire 400 androd 104 may be advanced through slot 150 in collar 112 and positionedbelow distal end of sleeve 244.

Portion 270 of movable member 252 may include threading. Threading ofportion 270 may engage threading in wall 246 of sleeve 244. Engagementof threading of portion 270 with threading in wall 246 may allow adistal end portion of movable member 252 to advance towards, or retractfrom, a distal end of sleeve 244 when the movable member is rotated.

In one embodiment, an inner sleeve may be positioned in a sleeve toinhibit translation and/or rotation of the sleeve relative to a collarof a bone fastener assembly. FIG. 21 depicts a cross-sectional view ofsleeve 244 with inner sleeve 272. A distal end of inner sleeve 272 maycontact an upper end of collar 112. A proximal portion of inner sleeve272 may engage a proximal portion of sleeve 244. The engagement mayallow inner sleeve 272 to apply a force against collar 112 that pressesflange 154 against flange 254 of sleeve 244 to inhibit translation ofthe sleeve relative to the collar. The engagement may be, but is notlimited to, a threaded connection, an interference fit, a frictionalfit, or a keyway type of connection. Wire 400 and rod 104 may beadvanced through slot 150 in collar 112 and positioned below distal endof sleeve 244.

In some embodiments, a distal end of an inner sleeve may be roughened ortextured to frictionally engage a proximal surface of the collar. Thefrictional engagement may inhibit rotation of the sleeve relative to thecollar. In some embodiments, inner sleeve 272 may include passage 274. Apin may pass through passage 274 into an opening in collar 112. When apin is positioned through passage 274 into the opening, rotation ofsleeve 244 relative to collar 112 may be inhibited.

In some embodiments, threading may be used to couple a detachable memberto a collar. FIG. 22 and FIG. 23 depict partial cross-sectionalrepresentations of sleeves 244 that couple to collars 112 by threadedconnections. Sleeves 244 may include female threading that iscomplementary to male threading of collar 112. In some embodiments,threading of the sleeve and threading of the collar may be modifiedthreads. Wire 400 and rod 104 may be advanced through slot 150 in collar112 and positioned below distal end of sleeve 244.

FIG. 24 depicts a partial cross-sectional representation of sleeve 244that couples to collar 112 by a threaded connection. Sleeve 244 mayinclude male threading, and collar 112 may include complementary femalethreading. Wire 400 and rod 104 may be advanced through slot 150 incollar 112 and positioned below distal end of sleeve 244. In someembodiments, portion 276 of collar 112 that includes threading whichmates with threading of sleeve 244 may be a break-off section. Collar112 may be held in a fixed position. Torque may be applied to sleeve 244to shear off portion 276.

In some embodiments, a detachable member may include a pair of hingedarms configured to couple to a collar. FIG. 25 and FIG. 26 depictembodiments of sleeves that include hinged portions. Sleeve 244 mayinclude arms 278. Arms 278 may be pivotally coupled together by hinge280. Hinge 280 may be located near a proximal end of sleeve 244. In somesleeve embodiments, sleeve 244 may include a locking element or abiasing element (e.g., a spring) near or at hinge 280. A locking elementor biasing element may cause a clamping force to be exerted on collar112 to maintain the collar in the sleeve and/or to inhibit rotation ofcollar 112 in sleeve 244. In some embodiments, such as in the embodimentdepicted in FIG. 25, flange 254 of sleeve 244 may contact a bottomportion of collar 112. Wire 400 and rod 104 may be advanced through slot150 in collar 112 and positioned above distal end of sleeve 244. In someembodiments, such as in the embodiment depicted in FIG. 26, flange 254of sleeve 244 may contact flange 154 of collar 112.

In some detachable member embodiments, proximal portions of detachablemembers may be chamfered to allow ends of the detachable members to moreclosely approach each other than detachable members with a uniform crosssection. FIG. 27 depicts sleeves 244 coupled to collars 112 engaged inadjacent pedicles 164, and rod 104 having a non-circular cross-sectionalprofile spanning between collars 112. Sleeves 244 may include chamferedsurfaces 282. Chamfered surfaces 282 may reduce space between proximalends of sleeves 244. During some surgical procedures, only one of thesleeves may be chamfered. During some surgical procedures, the use of asleeve with a chamfered surface may allow for smaller incisions thanrequired when using non-chamfered sleeves. In some embodiments, othertypes of detachable members may be used to reduce space between proximalends of detachable members. Other types of detachable members mayinclude, but are not limited to, detachable members of differentlengths, detachable members of different diameters, and detachablemembers with flexible end portions.

Detachable members may be of various lengths. Detachable members ofdifferent lengths may be used in the same surgical procedure. Adetachable member length used in a spine stabilization procedure may bedetermined by a patient's anatomy. Detachable members may be just shortenough to allow manipulation by a medical practitioner above an incisionin a patient. In some embodiments, detachable members may be about 3.5to about 11.5 cm long. For example, a single-channel detachable membermay be about 10 cm long. In some embodiments, detachable members may beabout 11.5 cm to about 14 cm long. For example, a single-channel or amulti-channel detachable member may be about 12.5 cm long. Amulti-channel detachable member may be longer than a single-channeldetachable member. In some embodiments, a multi-channel detachablemember may be at least about 15 cm long. For example, a multi-channeldetachable member may be about 16 cm long. Detachable members that aretoo long may require a longer incision and/or a larger tissue plane forinsertion of a spine stabilization system. Insertion of a rod may bemore difficult with detachable members that are longer than necessary.Detachable members with excess length may be bulky and hard tomanipulate during a surgical procedure.

A detachable member may be flexible over its entire length or include aflexible portion near a proximal end of the detachable member. Aflexible portion may allow positioning of a proximal portion of adetachable member in a desired location. A flexible portion may beproduced from any of various materials including, but not limited to, asurgical grade plastic, rubber, or metal. A flexible portion may beformed of various elements, including, but not limited to, a tube, achannel, or a plurality of linked segments.

FIG. 28 depicts one embodiment of sleeves 244 with a connection thatallows movement of first portion 284 relative to second portion 286.First portion 284 may be coupled to collar 112 of bone fastener assembly102, with rod 104 having a non-circular cross-sectional profile spanningbetween collars 112. Second portion 286 may connect to first portion 284at linkage 288. Linkage 288 may include, but is not limited to, alocking element, a pivot point, a hinge, or a pin. In some embodiments,the linkage may be a ball and socket type of connection that allowsrotational motion of second portion 286 relative to first portion 284.During some spine stabilization procedures, a detachable member withouta second portion that is able to move relative to a first portion may beused at one vertebra, and a detachable member with a second portion thatis able to move relative to a first portion may be used at one or morevertebrae that are to be stabilized.

When bone fasteners of polyaxial bone fastener assemblies are positionedin vertebral bone, detachable members coupled to collars of the bonefastener assemblies may be moved in desired positions. During surgery, adetachable member in a patient may be oriented towards an adjacentvertebra that is to be stabilized to reduce the required incision size.

In some embodiments, channels of detachable members may face a directionother than toward each other. FIG. 29 depicts sleeves 244 coupled tocollars 112 oriented at an angle so that channels 248 of sleeves 244face in different directions. In some embodiments, channels in thedetachable member may not be longitudinal channels down the length ofthe detachable member. In embodiments of detachable members withnon-longitudinal channels, the channels of two adjacent detachablemembers may not face towards each other when the openings of collarscoupled to the detachable members are aligned.

In one embodiment, a frame may couple to two or more detachable members.FIG. 30 depicts a perspective view of sleeves 244 coupled to frame 290.FIG. 30 further depicts rod 104 with a non-circular cross-sectionalprofile spanning between two collars 112. As used herein, a “frame”includes any of a variety of structural elements including, but notlimited, rods, bars, cages, or machined blocks. In some embodiments,frame 290 may provide a rigid coupling between sleeves 244. In otherembodiments, frame 290 may allow for angular or translational movementbetween sleeves. For example, frame 290 may include slidable elementsthat allow sleeves to be translated toward each other or away from eachother to facilitate compression or distraction of vertebrae.Alternatively, frame 290 may enable sleeves 244 to pivot toward eachother or away from each other. In some embodiments, frame 290 may allowfor movement of sleeves 244 to facilitate spinal reduction.

After a bone fastener assembly is coupled to a detachable member, adriver may be coupled to a bone fastener of the bone fastener assembly.The driver may be used to insert the bone fastener into vertebral bone.

FIG. 31 depicts one embodiment of driver 292 positioned in sleeve 244.Sleeve 244 is coupled to bone fastener assembly 102. Driver 292 may becoupled to collar 112 and to bone fastener 108 of bone fastener assembly102. Coupling driver 292 to collar 112 and to bone fastener 108 mayensure proper alignment of the driver relative to the bone fastener.Coupling driver 292 to collar 112 and to bone fastener 108 may alsoinhibit movement of collar 112 relative to bone fastener 108 duringinsertion of bone fastener 108.

Driver 292 may include outer shaft 294, inner shaft 296, and removablehandle 236. Outer shaft 294 may include threading 298 and texturedportion 300. A portion of outer shaft 294 may be positioned in a passagethrough sleeve 244 (passage 250 shown in FIG. 13). Threading 298 maycouple to a modified thread of collar 112. Textured portion 300 mayfacilitate rotation of outer shaft 294 so that threading 298 engages themodified thread of collar 112. When threading 298 engages the modifiedthread of collar 112, driver 292 may be securely coupled to bonefastener assembly 102, which is securely fastened to sleeve 244.

A distal end of inner shaft 296 may be coupled to bone fastener 108during use. Inner shaft 296 may be coupled at a proximal end toremovable handle 236 during use. Inner shaft 296 may be rotatablerelative to outer shaft 294 so that bone fastener 108 can be insertedinto vertebral bone. A proximal portion of inner shaft 296 may includeat least one flat portion that fits in a mating portion of removablehandle 236. Removable handle 236 may be the same removable handle thatis used with bone tap 592 that forms a threaded opening in vertebralbone for a bone fastener 108. Removable handle 236 may be removed fromdriver 292 during insertion of guide wire 218 through driver 292 so thatguide wire 218 may be held in at least one place at all times. In someembodiments, a removable handle for the driver may be unnecessary giventhe length of guide wire 218 and/or the length of the driver (e.g., along guide wire 218 and/or a short driver).

FIG. 32 depicts a cross-sectional representation of a portion of oneembodiment of a driver that is coupled to bone fastener 108 and collar112 of a bone fastener assembly. Collar 112 is coupled to sleeve 244.Sleeve 244 is positioned in dilator 302. In some embodiments, clearancebetween outer shaft 294 and sleeve 244 may be relatively small. In someembodiments, the clearance between outer shaft 294 and sleeve 244 mayrange from about 0.1 mm to about 0.75 mm. For example, the clearancebetween outer shaft 294 and sleeve 244 may be about 0.25 mm (i.e., aninner diameter of the sleeve may be about 0.5 mm greater than an outerdiameter of the outer shaft). Also, clearance between sleeve 244 anddilator 302 may be relatively small. The small clearances may inhibitundesired movement of the instruments relative to each other and/orreduce bulkiness at the surgical site.

Thread 298 of outer shaft 294 of the driver may couple to modifiedthread 148 of collar 112. Head 304 of inner shaft 296 of the driver maycouple to tool portion 126 of bone fastener 108. Head 304 may have acomplementary shape to tool portion 126 of bone fastener 108. Guide wire218 may be inserted into a distal end of passage 114 of bone fastener108 and through passage 306 of the driver. When guide wire 218 isinserted into passage 114 and passage 306, a removable handle may not becoupled to inner shaft 296.

In operation, wire 400 can be used to guide components from the exteriorof the patient via a first incision or a second incision to bonefastener assembly 102 advanced into the patient via a third insertionsuch that rod 104 can be guided under tissue and muscle to anothersleeve/collar assembly advanced into the patient via a fourth incision.A scalpel may be used to make an incision in the patient. Wire 400and/or rod 104 can be radiolucent or contain markers that allowplacement of wire 400 and rod 104 to be viewed under medical imagingsuch fluoroscopy.

FIG. 33 depicts a side view of one embodiment of rod 104 comprisingsegments 404. Segments 404 may connect to other segments 404 usingeither end, or may have one end for connecting with other segments 404and a second end shaped to ease passage through or under tissue 460. Insome embodiments, rod 104 can include rounded, beveled, tapered orotherwise shaped ends. First segment 404A may have a desiredcharacteristic, such as the curvature along its length as depicted inFIG. 33. In FIG. 33, first segment 404A may be engaged with wire 400such that a surface aligns with a surface of wire 400. Second segment404B may have a desired characteristic, such as the curvature along itslength depicted in FIG. 33. Second segment 404B may be engaged with wire400 such that a surface of second segment 404B aligns with a surface ofwire 400. When first segment 404A and second segment 404B are connectedto form rod 104 and attached to bone fastener assemblies 102, spinestabilization system 100 may have a desired overall curvature. Forexample, if segments 404A and 404B have the same curvature, indexingsecond segment 404B 180 degrees enables rod 104 to have a singlecurvature. Alternatively, if segments 404A and 404B are indexed 180degrees from each other, rod 104 may have an S-shaped configuration. Anadvantage to this embodiment is that an instrumentation kit may includerelatively few segments, and the surgeon need only index segments 404A,404B, etc., onto wire 400 to construct rod 104 having a selectedcurvature. While the characteristic of segments 404A and 404B aredescribed as curvatures with respect to FIG. 33, other characteristicsare possible, such as torsional stiffness, tensile strength, compressivestrength, hardness, biocompatibility, or the like. As shown in FIG. 33,rod 104 can have passage 406 along a portion thereof such that rod 104can be advanced along wire 400. In such one embodiment, wire 400 canfirst be run along insertion path 455 to assemblies 450A and 450B asshown in FIG. 33. Rod 104 can then be placed by guiding rod 104 usingwire 400 in passage 406.

FIGS. 34, 35, and 36 depict side views of segments 404 of rod 104, inwhich an end of segment 404 has a feature such as hole 407, groove 408,or notch 409 for attachment to wire 400 such that rod 104 can be pulledvia wire 400. FIG. 34 depicts a side view of one embodiment of segment404 having opening 407. FIG. 34 further depicts segment 404 having twocurves. FIG. 35 depicts a side view of one embodiment of segment 404having groove 408 extending about segment 404. FIG. 35 further depictssegment 404 having an angle. FIG. 36 depicts a side view of segment 404having notch 409. FIG. 36 further depicts segment 404 having a bend.Those skilled in the art will appreciate that there are other methodsfor using wire 400 to advance rod 104 or segments 404. In someembodiments, a bead or knot located on wire 400 may be larger thanpassage 406 in segment 404 such that tensioning wire 400 contacts a beador knot with segment 404 and further tensioning pulls segment 404 withwire 400.

FIGS. 37 and 38 illustrate embodiments for placement of rod 104 usingwire 400 and assemblies 450A and 450B. Various surgical tools can beused to position and move rod 104 along wire 400. Referring to FIG. 37,sleeve 244A can be advanced through a first incision I₁ in tissue 460and coupled to collar 112A to form assembly 450A, and sleeve 244B can beadvanced through a second incision I₂ in tissue 460 and coupled tocollar 112B to form assembly 450B. When sleeve 244A is in place, wire400 can be inserted into a third incision I₃ in tissue 460. As wire 400moves, it can displace tissue and muscle to define path 455. Wire 400may be advanced through openings 116 (not visible in FIG. 37) in collar112A and collar 112B, and advanced until wire 400 exits the patient viaa fourth incision I₄ in tissue 460. First segment 404 of rod 104 can beengaged to wire 400 so that a first portion of first segment 404 entersthe patient through the third incision I₃, advances along a path definedby wire 400, passes through a first side of assembly 450A, out theobverse side of assembly 450A, passes through a first side of assembly450B, and may pass out the obverse side of assembly 450B. As shown inFIGS. 37 and 38, wire 400 may pass through openings 116 in collar 112Aand 112B and rod 104 (or segments 404) can pass through openings 116 incollar 112A (shown in FIG. 37) and pass through openings 116 in collar112B. Segments 404 may be connected to form rod 104. Rod 104 can beoriented by rotating wire 400. Rod may be secured to bone fastenerassemblies 102, forming spine stabilization system 100 individuallysuited for the patient. Sleeves 244 may be uncoupled from collars 112and removed. Wire 400 may be withdrawn from the third incision I₃ oradvanced through the fourth incision I₄. Alternatively, wire 400 may becut or severed by a tool such that a portion of wire 400 remains in thebody. In one embodiment, leaving a portion of wire 400 inside rod 104may provide additional support for the spine.

After rod 104 has been positioned in collars 112 as desired, closuremembers may be used to secure rod 104 to collars 112. FIGS. 39A and 39Bdepict perspective views of driver 354. Driver 354 may be used toposition a closure member in a collar of a bone fastener assembly.

FIG. 40A depicts driver 354 with coupled closure member 106 positionedfor insertion in sleeve 244 to couple rod 104 having a non-circularcross-sectional profile to collars 112. After insertion of driver 354 insleeve 244, closure member 106 may be positioned proximate collar 112.With driver 354 positioned in sleeve 244, as shown in FIG. 40B, thedriver may be rotated to advance closure member 106 in collar 112 andsecure rod 104 to collar 112. When closure member 106 is snug and rod104 is secured, driver 354 may be disengaged from closure member 106 andremoved from sleeve 244. In one embodiment, driver 354 may be used tosecured closure member 106. In certain embodiments, driver 354 mayinclude a mechanism to dislodge a closure member and/or a tool portionof a closure member from the distal end of the driver.

In some embodiments, a detachable member may be held with a countertorque wrench as the tool portion of a closure member is secured. In oneembodiment, about 120 in-lbs of torque may be required to secure aclosure member. A counter torque wrench may inhibit transfer of force tothe patient when a closure member is being secured to a collar. FIG. 41depicts one embodiment of counter torque wrench 364 used to inhibitapplication of torque to a patient's spine during a closure member.Sleeve 244 may fit in opening 366 of counter torque wrench 364. Countertorque wrench 364 may be positioned near a proximal end of sleeve 244during use. Force may be applied to counter torque wrench 364 in adirection opposite to rotational force applied to driver 354 to secureclosure member 106. Opening 366 in torque wrench 364 may be of any shapeto accommodate a cross-sectional shape of sleeve 244 and inhibitrotation of the sleeve during use.

FIG. 42 depicts one embodiment of counter torque wrench 368 designed toaccommodate sleeves. Counter torque wrench 368 may include hollow shaft370 and handle 372. Groove 374 may be located at a distal end of hollowshaft 370. FIG. 43 depicts counter torque wrench 368 fitted overmulti-channel sleeve 244. In one embodiment, hollow shaft 370 may beinserted through an opening in the body over sleeve 244 and advancedtoward the spine until rod 104 is seated in groove 374. Counter torquewrench 368 may engage the spine stabilization system. Force may beapplied to counter torque wrench 368 in a direction opposite torotational force applied to a driver used to secure closure member 106.During a minimally invasive spine stabilization procedure, countertorque wrench 368 may be used with various types of detachable members,including single-channel sleeves and multi-channel sleeves.

Minimally invasive procedures may involve locating a surgical site andpositions for four skin incisions to access the surgical sites. Firstand second incisions may be located above vertebrae to be stabilized.Third and fourth incisions may be located along the spine some distancefrom the first and second incisions. An opening in the tissue under theskin may be enlarged to exceed the size of the skin incisions. Movementand/or stretching of an incision and angulation of collars of bonefastener assemblies may allow the length of the incision to beminimized. In some embodiments, minimally invasive insertion of a spinestabilization system may not be visualized. In certain embodiments,insertion of a spine stabilization system may be a top-loading,mini-opening, muscle-splitting, screw fixation technique.

In one embodiment of a spine stabilization system insertion method, thepatient may be placed in a prone position on a radiolucent table withclearance available for a C-arm of a fluoroscope. For example, a Jacksontable with a radiolucent Wilson frame attachment may be used. Theability to obtain high quality images is very important. Bolsters,frames, and pads may be inspected for radiolucency prior to theoperation. Placing the patient in a knee-chest position (e.g., using anAndrews table) should be avoided. Care should be taken to avoid placingthe patient's spine in kyphosis during positioning of the patient.

The C-arm of the fluoroscope should be able to freely rotate between theanteroposterior, lateral, and oblique positions for optimalvisualization of pedicle anatomy during the procedure. The arm should berotated through a full range of motion prior to beginning the procedureto ensure that there is no obstruction or radio-opaque object in theway. The fluoroscope may be positioned so that Ferguson views and“bullseye” views are obtainable. Once the patient is positioned and theability to obtain fluoroscopic images of the target levels forinstrumentation has been confirmed, the patient may be prepared anddraped sterilely.

For most of the lumbar region, the vertebral pedicle is an obliquelyoriented cylindrical corridor. The angulation varies by approximately 5degrees per level (e.g., L1: 5 degrees; L5: 25 degrees). A pre-operativefine-cut computed tomography image may be examined to determine anyunique anatomy of the patient. Acquiring the pedicle in the most lateraland superior quadrant of the pedicle may be desirable to avoid theoverriding facet during a minimally invasive procedure. A lateral entrypoint may allow for better screw convergence as well as lessinterference with the superior adjacent level facet joint. A targetingneedle may be passed in a medial and inferior trajectory, thus followingthe natural pathway of the pedicle. Frequent fluoroscopic inspection inboth an anteroposterior and lateral plane may ensure proper passage ofthe needle as the needle is inserted into vertebral bone.

Various techniques may be used to plan the skin incisions and entrypoints. In one embodiment, the planning sequence for single-levelstabilization may include the following four steps. First, ananteroposterior image may be obtained with the spinous processescentered at the target vertebral bodies. Vertical lines passing throughmidpoints of pedicles that are to receive bone fasteners may be markedon the patient. The lines do not represent skin entry points. The linesare markers of pedicle entry points used to estimate angles at whichtargeting needles to be inserted to contact the pedicles. In someembodiments, sets of vertical lines may be drawn corresponding to thelateral edges of the pedicles instead of lines corresponding to themidpoints of the pedicles.

Second, horizontal lines may be marked approximately through the centersof the pedicles (mid-pedicle lines) on the patient. In some embodiments,the lines may be drawn on the superior side of the center axes (superiorto the mid-pedicle).

Third, an oblique or “bullseye” view (i.e., down a longitudinal axis ofa pedicle) may be obtained on each side of the patient for each pediclethat is to be stabilized. Vertical oblique view lines may be marked onthe skin at the midpoints of each of the pedicles that are to receive abone fastener. The oblique view lines may be drawn in a different colorthan the vertical lines drawn during the first step. In someembodiments, vertical lines may be drawn corresponding to the lateraledges of the pedicles instead of lines corresponding to the midpoints ofthe pedicles.

The oblique view lines may be about 2 cm to about 3 cm away from thelateral pedicle border lines marked in the first step. For largerpatients, the oblique view line may be greater than about 3 cm away fromthe midline marked in the first step. For smaller patients, the obliqueview line may be closer than about 2 cm away from the midline marked inthe first step. The intersection of the oblique view lines with thehorizontal lines drawn in the second step may represent skin entrypoints for a targeting needle as the targeting needle passes throughsoft tissue at an angle towards the bony pedicle entry point. A sidefluoroscopic image, the horizontal lines, and the vertical lines mayhelp the surgeon triangulate between the skin entry points and bonyentry points.

Fourth, an incision may be made in the skin between mid-pedicle linesalong the vertical oblique view lines. The skin incision may be fromabout 2 cm to about 4 cm long. In some embodiments, the incision may befrom about 2.5 cm to about 3 cm long. Limiting the length of theincision may enhance patient satisfaction with the procedure. Theincisions may be pre-anesthetized with, for example, 1% lidocaine with1:200,000 epinephrine. To blunt the pain response, a long spinal needlemay be used to dock on the bone entry point and inject the plannedmuscle path in a retrograde fashion as well. Once the incision has beenmade, tissue surrounding the incision may be pulled and/or stretched toallow access to a target location in a vertebra.

After sterile preparation and draping, the pedicle entry points may befluoroscopically rechecked to ensure that the previously marked linescorrespond to the intersection of the midline of the transverse processand the lateral joint and pars interarticularis. The intersection of thefacet and the transverse process provides a starting point that may helpavoid the canal and follow the natural inclination of lumbar pedicles.For the spine stabilization system described, in which sleeves coupledto bone fastener assemblies are substantially unconstrained by insertionangles of the bone fasteners, patient anatomy may determine the mostadvantageous insertion angles of the bone fasteners.

A scalpel may be used to make a stab wound at the junction of an obliqueview line and a mid-pedicle line. In one embodiment, the scalpel may bea #11 scalpel. A targeting needle may be passed through the incision inan oblique lateral to medial trajectory towards the bony entry pointdefined by a lateral pedicle border line. The C-arm of the fluoroscopemay be placed in an anteroposterior position for this maneuver.

Insertion of a spine stabilization system may include graduallyincreasing the diameter of an opening formed in a pedicle and/orvertebral body to accept a bone fastener assembly. For example, atargeting needle may have outer diameter of about D. A bone awl insertedafter the targeting needle may have an outer diameter incrementallylarger than the outer diameter of the targeting needle. As used herein,an incrementally larger diameter may be large enough to allow a snug butadjustable fit. For example, the bone awl may have outer diameter ofabout (D+x). A tap portion of a bone tap inserted after the bone awl mayhave a minor diameter of about (D+2x). A bone fastener may have a minordiameter of about (D+3x). In some embodiments, x may be between about0.1 mm and about 1.0 mm. For example, x may be about 0.5 mm. Incrementalsizing of the targeting needle, bone awl, tap, and bone fastener maypromote a proper fit of the bone fastener in the vertebra to bestabilized.

As the targeting needle encounters the bony anatomy, anteroposteriorfluoroscopic images may be used to place the tip of the needle at theupper outer quadrant of the pedicle. In some embodiments, the needle maybe walked medially along the transverse process to the pedicle entrypoint. In some embodiments, the needle tip may be docked by lightlytapping the tip into the bone with a mallet or other impact device todrive the tip into the bone. In some embodiments, the needle tip may bedocked by applying downward pressure to the targeting needle to forcethe tip into the bone.

The fluoroscope may then be moved to a lateral position. The surgeon maycorrect the sagittal trajectory of the needle by moving the needle in ananterior or posterior direction to match the vector of the pediclecorridor. In some embodiments, a mallet or other impact device may beused to gently advance the targeting needle into the pedicle halfway tothe pedicle-vertebral body junction. In other embodiments, force may beapplied to the targeting needle to drive the targeting needle into thepedicle halfway to the pedicle-vertebral body junction. Ananteroposterior image may then be obtained to confirm that the needle isapproximately halfway across the pedicle in the anteroposterior view. Ifthe tip is more than halfway across the pedicle in a lateral to medialprojection, the trajectory may be too medial. Further advancement of theneedle may risk passing the needle through the spinal canal. The needlemay be repositioned. A new starting point or new trajectory may beobtained. If the anteroposterior image demonstrates that the needle issignificantly lateral in the pedicle, then the needle may have passedalong the lateral portion of the pedicle. A needle that has passed alongthe lateral portion of the pedicle may be withdrawn and repositioned.

Once a good trajectory has been obtained, the targeting needle may beadvanced using a mallet. In some embodiments, the needle may be pushedin without a mallet. The targeting needle may be advanced to thejunction of the pedicle and vertebral body under lateral fluoroscopicguidance. FIG. 44A depicts targeting needle 198 advanced to the junctionof pedicle 164. At this point, confirmation of position and trajectoryshould be repeated under anteroposterior fluoroscopy. Targeting needle198 may be further advanced to a desired depth within vertebral body 166using a mallet or applied force. FIG. 44B depicts targeting needle 198advanced to the desired depth.

A scale on targeting needle 198 may be used to approximate a length of abone fastener to be used. A first depth of targeting needle 198 may bemeasured relative to body surface 376 when pedicle 164 is firstencountered. A second depth of targeting needle 198 may be measuredrelative to body surface 376 after the targeting needle has beenadvanced to the desired depth in vertebral body 166. An approximatelength of the pedicle screw to be used may be determined by taking adifference between the depth measurements.

After targeting needle 198 has been advanced into the bone, member 202of the targeting needle (shown in FIG. 44B) may be removed from thetargeting needle. FIG. 44C depicts outer housing 200 with the memberremoved. After removal of the member, guide wire 218 may be placedthrough a passage in targeting needle 198 into vertebral body 166. FIG.44D depicts targeting needle 198 with guide wire 218 positioned throughthe passage in the targeting needle. Lateral fluoroscopic images may beobtained to indicate the position of guide wire 218. In someembodiments, guide wire 218 may be pushed into vertebral body 166. Incertain embodiments, guide wire 218 may be advanced about 1 cm beyond anend of outer housing 200 to secure the guide wire in vertebral body 166.In some embodiments, a small diameter tissue dilator may be placed overguide wire 218 and positioned on an upper surface of the targetingneedle. The tissue dilator may provide stability to guide wire 218.Added stability from the dilator may allow guide wire 218 to besuccessfully tapped into the vertebral body with a small mallet. Careshould be taken to avoid kinking guide wire 218. After guide wire 218 issecured in vertebral body 166, outer housing 200 may be removed from thepatient. FIG. 44E depicts guide wire 218 after removal of the targetingneedle.

Once guide wire 218 has been passed through the targeting needle and thetargeting needle has been removed, guide wire 218 may be used as a guideto position one or more successively sized dilators around a targetlocation in a pedicle. A dilator may be a conduit with a regular shape(e.g., cylindrical) or an irregular shape (e.g., C-shaped). A dilatormay form an opening through soft tissue to the pedicle. For patientswith a thick fascia, it may be advantageous to make a nick in the fasciawith a scalpel blade to facilitate passage of the dilators. The dilatorsmay be passed sequentially over guide wire 218. The dilators may berotated during insertion to facilitate dilation of surrounding tissue.The dilators may be inserted until the leading edges contact thepedicle. A distal end of a dilator may be tapered to facilitatepositioning of the dilator proximate the pedicle. An instrumentation setfor a spine stabilization system may include two, three, four, or moresuccessively sized dilators.

FIG. 45A depicts first dilator 302A positioned around guide wire 218.First dilator 302A may have an inner diameter just slightly larger thanan outer diameter of guide wire 218. As used herein, “an inner diameterjust slightly larger than an outer diameter” may mean that the innerdiameter is between about 0.03 mm and about 1.0 mm greater than theouter diameter. For example, an inner diameter of first dilator 302A maybe about 0.5 mm greater than the outer diameter of guide wire 218.

FIG. 45B depicts second dilator 302B positioned around first dilator302A. Second dilator 302B may have an inner diameter just slightlylarger than an outer diameter of first dilator 302A.

FIG. 45C depicts third dilator 302C and fourth dilator 302D andpositioned around second dilator 302B. Third dilator 302C may have aninner diameter just slightly larger than an outer diameter of seconddilator 302B. Fourth dilator 302D may have an inner diameter slightlylarger than an outer diameter of third dilator 302C. Once fourth dilator302D is in position, dilators 302A, 302B, 302C may be removed, startingwith dilator 302A. Lengths of dilators in a successively sized set maydecrease with increasing diameter to facilitate removal of the smallerdilators. Care should be taken to avoid dislodging guide wire 218 duringinsertion and removal of the dilators. FIG. 45D depicts fourth dilator302D positioned around guide wire 218 following removal of dilators302A, 302B, 302C.

After tissue dilation has been achieved, a large diameter dilator (e.g.,third dilator 302C or fourth dilator 302D shown in FIG. 45C) may be usedto guide a bone fastener assembly and/or insertion instruments toward atarget location in a pedicle. FIGS. 46A-46F depict portions of aprocedure for preparation of pedicle 164 and vertebral body 166 forreceiving a bone fastener assembly. FIG. 46A depicts bone awl 591positioned over guide wire 218 in dilator 302 such that a tip of thebone awl is on or near a surface of pedicle 164. Bone awl 591 may bedriven downwards into pedicle 164 to breach cortical bone of thepedicle. FIG. 46B depicts a position of bone awl 591 after pedicle 164has been breached. After pedicle 164 is breached, bone awl 591 may beremoved from dilator 302. FIG. 46C depicts guide wire 218 and dilator302 after removal of bone awl 591. In some embodiments, an initialpassage may be formed in the pedicle and the vertebral body using adrill or a drill and tap combination.

FIG. 46D depicts tap 592 positioned in dilator 302. After pedicle 164 isbreached, tap 592 may be inserted over guide wire 218 into dilator 302.In one embodiment, dilator 302 may be third dilator 302C. Tap 592 may besized to fit snugly inside third dilator 302C. In some embodiments,dilator 302 may be fourth dilator 302D. In certain embodiments, fourthdilator 302D may be inserted over third dilator 302C after bone has beentapped through the third dilator. Tapping through third dilator 302Crather than fourth dilator 302D may introduce less bulk at the targetsite of a pedicle during the tapping procedure. In some embodiments, anouter diameter of a sleeve coupled to a bone fastener assembly to beinserted in the pedicle may be substantially the same as an outerdiameter of third dilator 302C.

Tap 592 may include removable handle 236 and indicia 240. Indicia 240may be a scale. When tap 592 is positioned such that a first threadflight contacts pedicle 164, a first measurement of the position of thetap relative to a top of dilator 302 using indicia 240 may be noted. Tap592 may be rotated to form a threaded passage through pedicle 164 andinto vertebral body 166 to a desired depth. In some embodiments, alength of the threaded portion of tap 592 may be used to determine adepth of a threaded passage formed in a bone. For a threaded portion ofa known length (e.g., 30 mm, 45 mm, 60 mm), a scaled image (e.g., X-rayimage) of a depth of the threaded portion in a bone monitored duringtapping may allow a medical practitioner to determine the depth of thethreaded passage. In some embodiments, tap 592 may form threads of majordiameter about 0.5 mm smaller than a major diameter of threads of a bonefastener to be inserted into the threaded passage.

FIG. 46E depicts a position of tap 592 after a threaded passage of adesired length has been formed in pedicle 164 and vertebral body 166.Care should be exercised to ensure that guide wire 218 is not bent orkinked during the tapping process. The position of tap 592 relative tothe end of guide wire 218 may be monitored to ensure that guide wire 218is not dislodged or removed from the vertebra. In some embodiments, aposition of tap 592 may be monitored using fluoroscopic imaging.

After a threaded passage of a desired length has been formed in pedicle164 and vertebral body 166, a second measurement of the position of tap592 relative to a top of dilator 302 using indicia 240 may be noted. Alength of a threaded member may be determined by taking a differencebetween the first and second measurements. In some embodiments, anestimate of length may be derived based upon fluoroscopic images and aknown length of the tap that is visibly recognizable in the fluoroscopicimages. Tap 592 may be removed from vertebral body 166 and pedicle 164by rotating the tap out of the vertebral body and the pedicle. Handle236 may be removed from a blade portion of tap 592. The blade portion oftap 592 may be removed from guide wire 218 with control of guide wire218 initially maintained from above the tap and then from below the tap.Care may be taken when tap 592 is removed to maintain guide wire 218 inposition and to avoid damage of guide wire 218. FIG. 46F depicts dilator302 and guide wire 218 after removal of the tap.

A bone fastener assembly with a bone fastener of an appropriate lengthmay be selected for insertion in a patient. The size of the bonefastener may be verified with measurement indicia in an instrumentationset. In some embodiments, measurement indicia may be etched or printedon a portion of an instrumentation set. For example, the chosen bonefastener embodiment may be placed over the outline of a bone fastenerembodiment printed on a tray of the instrumentation set.

The chosen bone fastener assembly may be attached to a detachablemember. In one embodiment, a bone fastener assembly may be rotated on aflange of a detachable member. Movable members of the detachable membermay be extended into indentations in a collar of the bone fastenerassembly. A driver may be used to extend the movable members to couplewith the collar. When the bone fastener assembly is coupled to thedetachable member, a drive portion of a fastener driver may be coupledto a tool portion of the bone fastener. A shaft of the fastener drivermay be positioned in the passage of the detachable member. A removablehandle may be attached to the shaft of the fastener driver. Thedetachable member, collar, and bone fastener may be substantiallyco-axial when the fastener driver is positioned in the detachablemember. In some embodiments, the removable handle may be attached to theshaft of the fastener driver after the bone fastener, collar, detachablemember, and fastener driver combination is positioned down guide wire218 through a dilator and against a pedicle.

FIGS. 47A-47D depict portions of a procedure for inserting a bonefastener assembly into a patient. Driver 292 (coupled to the bonefastener), and sleeve 244 (coupled to the collar of the bone fastenerassembly) may be inserted along guide wire 218 into dilator 302. Forspine stabilization procedures using four successively sized dilators,dilator 302 may be fourth dilator 302D. Guide wire 218 represents thetrajectory that a bone fastener or bone fastener assembly may followtoward pedicle 164 during insertion of a spine stabilization system. Insome embodiments, tissue surrounding the incision may be pulled and/orstretched to allow a desired angular orientation of the bone fastenerassembly relative to pedicle 164. FIG. 47A depicts driver 292 and sleeve244 positioned in dilator 302. After insertion of the bone fastenerassembly, sleeve 244, and driver 292 in dilator 302, the driver may berotated to thread the bone fastener into pedicle 164 and vertebral body166. The bone fastener may be advanced into the pedicle underfluoroscopic guidance to inhibit breaching of the pedicle walls. Whenthe tip of the bone fastener advances beyond the posterior margin ofvertebral body 166, guide wire 218 may be removed to inhibit inadvertentbending of guide wire 218 or unwanted advancement of guide wire 218.

The bone fastener may be advanced to bring the collar down snug to thefacet joint. The bone fastener may then be backed off about a quarter ofa turn. Backing the fastener off about a quarter of a turn may allow forfull motion of the collar relative to the bone fastener. FIG. 47Bdepicts driver 292 after the bone fastener has been advanced to thedesired depth. After the bone fastener has been advanced to the desireddepth, driver 292 may be removed from the head of the bone fastener andfrom dilator 302. FIG. 47C depicts dilator 302 and sleeve 244 afterremoval of the driver. After removal of the driver, dilator 302 may beremoved from the patient. FIG. 47D depicts collar 112 of bone fastenerassembly and sleeve 244 after removal of the dilator.

After the bone fastener has been secured to the vertebra and the driverhas been removed from the sleeve, the polyaxial nature of the collar mayallow angulation of the sleeve relative to the bone fastener. Tissuesurrounding the incision may be released such that the sleeve is angledtoward a central location between vertebrae to be stabilized. The sleevemay be moved to facilitate positioning of instruments and/or tofacilitate access to the adjacent vertebra that is to be stabilized. Forexample, the sleeve may be tilted towards the adjacent pedicle so thatadditional length of an opening in the patient is not needed. Thechannel in the sleeve may be turned toward the adjacent pedicle that isto be stabilized with the spine stabilization system being formed.

A rod may be cut to length and contoured as desired. For example, amedical practitioner may use experience and judgment to determinecurvature of a rod for a patient. A desired curvature for the rod may bedetermined using fluoroscopic imaging. In some embodiments, a curvatureof the rod may be chosen such that, when the rod is secured to thecollars of the bone fastener assemblies, sleeves coupled to the bonefastener assemblies cross at a surface of the skin. Crossing of thesleeves at a surface of the skin allows the medical practitioner tominimize trauma to a patient by minimizing incision length and tissueplane area. The rod may be bent or shaped with a tool (e.g., a rodbender) to allow insertion of the rod through channels of sleeves withvarious spatial locations and/or various angular orientations.

Rods may have shapes including, but not limited to, straight, bent,curved, s-shaped, and z-shaped. FIG. 48 depicts one embodiment ofS-shaped rod 104. FIG. 49 depicts one embodiment of rod 104 in which thecurvature of rod 104 may be configured with any radius within a range ofradii. In some embodiments, the curvature of rod 104 may have multiplecurves of different radii (for example, multiple level stabilizations).FIG. 50 depicts one embodiment of bent rod 104. FIG. 51 depicts oneembodiment of straight rod 104. In some embodiments, rods 104 may have asubstantially circular longitudinal cross section. In certainembodiments, rods 104 may have other cross-sectional shapes including,but not limited to, regular shapes (oval, rectangular, rhomboidal,square) and irregular shapes. An instrumentation kit for a spinestabilization system may include straight rods and/or pre-shaped rods.Straight rods and/or pre-shaped rods may be contoured to accommodatepatient anatomy if needed during the surgical procedure.

With the rod satisfactorily positioned, the rod may be secured in placewith closure members. To ensure alignment of thread of closure memberwith thread of collar, the driver may initially be rotated in adirection that would result in removal of the closure member from thecollar. When the user of the driver feels engagement of threading of theclosure member with threading of the collar, the user may reverse thedirection of rotation of the driver to secure the closure member to thedriver. The closure member may secure the rod to the collar. Sleeve 244Amay serve as a coaxial guide to inhibit cross-threading during insertionof closure members 106. When the closure members are snug and rod 104 issecured, collars 112 are angled such that slots in the collars aresubstantially perpendicular to the rod. Driver 354 may be disengagedfrom the closure member and removed from sleeve 244.

In some embodiments, counter torque wrench 368 shown in FIG. 42 may beused to inhibit application of torque to a patient's spine. Countertorque wrench sleeve 370 may be inserted through the opening in the bodyover sleeve 244. Counter torque wrench sleeve 370 may be advanced towardthe spine until rod 104 is seated in groove 374 of the counter torquewrench sleeve. Force may be applied to counter torque wrench 368 in adirection opposite to rotational force applied to a driver used tosecure a closure member.

After a closure member is successfully secured to a collar, the drivermay be removed from the sleeve coupled to the anchored bone fastenerassembly. FIG. 52A depicts an assembled spine stabilization systemfollowing removal of driver 354 and wire 400. Key 262, shown in FIG.52B, may be used to rotate movable members in sleeves 244A, 244B.Rotation of movable members in sleeves 244A, 244B may release themovable members from the collars. Thus, sleeves 244A, 244B may beuncoupled from the collars above the incision. FIG. 52C depictsassembled spine stabilization system 100 following removal of sleeve244A. FIG. 52D depicts assembled spine stabilization system 100 coupledto adjacent pedicles following removal of sleeve 244B.

A spine stabilization system may be used to stabilize two or morevertebral levels (i.e., at least three adjacent vertebrae). In oneembodiment, an incision may be made in the skin between the outermostvertebrae to be stabilized. A first bone fastener assembly may becoupled to a first sleeve. The first bone fastener may be threaded intoa first pedicle at a target location such that the first sleeve extendsabove the body surface. The first sleeve may rotate about the head ofthe first bone fastener. A second bone fastener assembly may be coupledto a second sleeve and threaded into the second pedicle through a secondincision. A third bone fastener assembly may be coupled to a thirdsleeve and threaded into the third pedicle through a third incision.

In one embodiment of a method for a two-level spine stabilizationprocedure, three incisions may be made above three target locations overthree pedicles. A first bone fastener may be anchored to the middlepedicle. After the first bone fastener is secured, second and third bonefasteners may be coupled to outer pedicles as desired by advancing thesecond and third bone fastener assemblies via second and third incisionsto outer pedicles. A wire may be inserted into the patient via a fourthincision and advanced through the bone fastener assemblies. A rod or twoor more segments forming a rod may be advanced via the fourth incisionand passed through the collars. After a rod has been positioned andseated in collars as desired, closure members may be used to secure therod to the collars. One or more counter torque wrenches may be usedduring shearing of the tool portions of the closure members. In oneembodiment, counter torque wrench 364, depicted in FIG. 42, may be usedwith sleeves 244. Counter torque wrench 368, depicted in FIG. 43, may beused with multi-channel sleeves and/or single-channel sleeves.

Further modifications and alternative embodiments will be apparent tothose skilled in the art in view of this description. Accordingly, thisdescription is to be construed as illustrative only and is for thepurpose of teaching those skilled in the art the general manner ofcarrying out the teachings of the disclosure. It is to be understoodthat the embodiments shown and described herein are to be taken as thepresently preferred embodiments. Elements and materials may besubstituted for those illustrated and described herein, parts andprocesses may be reversed, and certain features may be utilizedindependently, all as would be apparent to one skilled in the art afterhaving the benefit of this disclosure. Changes may be made in theelements described herein without departing from the spirit and scope ofthe following claims.

1. A system for stabilizing a portion of a spine, comprising: a rodhaving a non-circular cross-sectional profile and a length to spanbetween two vertebrae; two bone fastener assemblies, wherein each bonefastener assembly comprises: a pedicle screw for advancement into avertebra; a collar for coupling the rod to the pedicle screw,comprising: two upwardly extending walls forming a passage having aprofile for receiving a portion of the rod non-circular cross-sectionalprofile; and a threaded portion; and a threaded closure member forengaging the threaded portion of the collar to couple the rod in thepassage; and a wire for percutaneous advancement of the rod to thepassage in a bone fastener assembly coupled to a vertebra, wherein thewire comprises a non-circular cross-sectional profile complementary tothe rod non-circular cross-sectional profile for engaging the rod toinhibit rotational movement of the rod relative to the wire.
 2. Thesystem of claim 1, wherein the rod non-circular cross-sectional profilecomprises an array of surfaces.
 3. The system of claim 1, wherein therod non-circular cross-sectional profile comprises a flange.
 4. Thesystem of claim 1, wherein the rod non-circular cross-sectional profilecomprises a slot.
 5. The system of claim 1, wherein the rod comprises acannulated passage along a length thereof.
 6. The system of claim 1,wherein the rod comprises a recessed portion along a length thereof. 7.The system of claim 1, wherein the rod comprises: two segments, whereineach segment comprises: a complementary non-circular cross-sectionalprofile for engaging the non-circular cross-sectional profile of thewire to inhibit rotational movement of the segment relative to the wire;a surface for engagement with a collar; a leading end for displacingtissue during advancement of a segment along the wire; and a trailingend comprising an engagement feature for connecting with an adjacentsegment, wherein connecting the two segments forms a rod, whereinconnecting the two segments of the rod to the two bone fastenerassemblies spans a vertebral level.
 8. The system of claim 7, whereineach segment comprises a passage through a portion thereof.
 9. Thesystem of claim 8, wherein the passage extends along a central axis. 10.The system of claim 8, wherein the passage is offset from a centralaxis.
 11. The system of claim 8, wherein the passage is oriented askewto a longitudinal axis.
 12. The system of claim 1, wherein the rodcomprises: a curvature along a length thereof; and a recessed portionlocated along the length and oriented transverse to the longitudinalaxis; and wherein the wire comprises a cross-sectional profile and acurvature for engaging the recessed portion.
 13. The system of claim 12,wherein the recessed portion comprises a passage through a portion ofthe rod and oriented at a selected angle relative to the longitudinalaxis.
 14. The system of claim 12, wherein the recessed portion comprisesa groove extending around at least a portion of the outer surface. 15.The system of claim 1, wherein the passage comprises a first passage forreceiving a portion of the wire and second passage for receiving aportion of the rod, wherein engaging the closure member in the collarwhen a wire is positioned in the first passage and when a rod ispositioned in the second passage couples the bone screw to the wire andthe rod.
 16. The system of claim 1, wherein the passage comprises afirst passage for receiving a portion of the wire and second passage forreceiving a portion of the rod, wherein engaging the closure member inthe collar when a wire is positioned in the first passage and when a rodis positioned in the second passage couples the bone screw to the rodand provides clearance for withdrawal of the wire from the bone screw.17. A method for stabilizing a portion of a spine, comprising the stepsof: making a first incision for anchoring a first bone fastener assemblyin a first vertebra, wherein a bone fastener assembly comprises: a bonescrew comprising: a threaded shank for engaging a portion of a vertebra;and a head portion connected to the threaded shank; and a collarcomprising: a bottom portion having an opening for receiving a portionof a bone screw; and two upwardly extending walls forming a firstpassage for receiving the rod and forming a second passage for receivinga portion of a wire; a threaded portion; and a threaded closure memberthreaded for engaging the threaded portion of the collar; making asecond incision for anchoring a second bone fastener assembly in asecond vertebra; making a third incision for entry of a wire comprisinga non-circular cross sectional profile; making a fourth incision forexiting of the wire; advancing the wire through the third incision forpositioning near the first and second bone fastener assemblies; engaginga rod with the wire, wherein the rod comprises: a non-circularcross-sectional profile, wherein the rod non-circular cross-sectionalprofile is complementary to the wire non-circular cross-sectionalprofile for engaging the wire to inhibit rotational movement of the rodrelative to the wire; rotating the wire to rotate the rod; and securingthe rod to the first and second bone screws, wherein the rod spans atleast one vertebral level.
 18. The method of claim 17, wherein the rodcomprises two or more segments, wherein the method comprises: engaging afirst segment of a rod to the wire, wherein each segment comprises: acomplementary non-circular cross-sectional profile for engaging thenon-circular cross-sectional profile of the wire to inhibit rotationalmovement of the segment relative to the wire; a surface for engagementwith a collar; a leading end for displacing tissue during advancement ofa segment along the wire; and a trailing end comprising an engagementfeature for connecting with the leading end of an adjacent segment,wherein connection of one or more segments of the rod to two or morecollars spans one or more vertebral levels; advancing the first segmentalong the wire to a second passage in the first collar; engaging asecond segment of the rod to the wire; advancing the second segment to asecond passage in the second collar; and connecting the leading end ofthe second segment with the trailing end of the first segment to span avertebral level with a rod having first and second curvatures.
 19. Amethod for advancing a rod into a body, comprising: advancing a firstbone fastener assembly via a first incision in the body, wherein a bonefastener assembly comprises: a bone screw having a threaded portion anda head portion; and a collar comprising a opening for receiving the headportion of the bone screw and an opening oriented transverse to theopening for receiving the head portion; anchoring the first bonefastener assembly to a first vertebra; advancing a second bone fastenerassembly via a second incision in the body; anchoring the second bonefastener assembly to a second vertebra; advancing a wire into the bodyvia a third incision, wherein the wire comprises a non-circularcross-sectional profile; advancing the wire through the transverseopenings in the first and second bone fastener assemblies to define apath; advancing the wire out of the body via a fourth incision; engaginga rod with the wire, wherein a rod comprises a non-circularcross-sectional profile complementary to the wire cross-sectionalprofile; and advancing the rod through the transverse openings in thefirst and second bone fastener assemblies along the path, wherein a rodcomprises a non-circular cross-sectional profile complementary to thewire cross-sectional profile, wherein the wire maintains radialorientation of the rod during advancement along the wire.
 20. The methodof claim 19, wherein the rod comprises a passage along a portionthereof, wherein the step of advancing the rod comprises moving the rodalong the wire.
 21. The method of claim 19, wherein the rod comprises anattachment feature for attaching the rod to the wire, wherein the stepof advancing the rod comprises moving the wire.
 22. The method of claim19, wherein the step of advancing the rod comprises advancing the rodfrom the third incision to the fourth incision.
 23. The method of claim19, wherein the step of advancing the rod comprises advancing the rodfrom the fourth incision to the third incision.
 24. The method of claim19, wherein the rod comprises two segments, wherein each segmentcomprises: a surface for engagement with a collar; a leading end fordisplacing tissue during advancement through the body; and a trailingend comprising a connection feature for connecting with an adjacentsegment, wherein connecting the two segments forms a rod, whereinengaging the two connected segments to the two bone fastener assembliesspans a vertebral level.